Curious what part of the EBL documentation you are referring to, so that it can be corrected in the future. Anyway, I did a deep dive on what you posted and this is what came up, which makes sense and appears the forum is correct. Have a look.The key technical explanation was captured in the search snippet. Here's a clear breakdown of what's actually correct:

The Documentation is Wrong (or at best, misleading) — The Forum Consensus is Right

Your intuition is correct, and so is the forum thread. Here's the precise technical explanation:

How the Lag Filter Actually Works

The ECM reads the TPS sensor and lag-filters it every 12.5 milliseconds (80 times per second). The filter coefficient controls how quickly the filtered output chases the raw input. Third Generation F-Body Message Boards

The math that matters: Delta TPS = Current TPS − Lagged (filtered) TPS

This delta value is what drives AE. So:

• Smaller coefficient → slower filter → output lags further behind input → LARGER delta → more AE, sooner and longer
• Larger coefficient → faster filter → output catches up quickly → SMALLER delta → less AE

A smaller filter coefficient causes the output of the filter to be slower to catch up to the input. This increases the duration of the AE. With a slower filter (smaller coefficient), the delta will also be greater, providing a larger volume of AE. Third Generation F-Body Message Boards

So What's Wrong With the Documentation?

The documentation statement — "A smaller value will be a greater lag" — is technically correct on its own. A smaller coefficient does produce greater lag. The problem is the phrasing implies this is a bad thing or means AE comes in slower, when in fact greater lag = larger delta TPS = AE kicks in harder and faster from the tune's perspective.

The forum saying "lower the value to make AE come in sooner" is correct in practice — lowering the coefficient increases the lag between raw and filtered TPS, which inflates the delta, which triggers a stronger AE response.

For Your XDF Description

Here's how I'd word it accurately:
AE TPS Filter Coefficient (vs. Coolant Temp): Controls the lag rate of the TPS filter used to calculate delta TPS for AE. A smaller value = more lag = larger delta TPS = stronger and longer AE. A larger value = less lag = smaller delta = weaker, shorter AE. Affects both the magnitude and duration of TPS-based AE.
Smaller filter values result in larger delta TPS values, impacting the AE threshold, volume, and duration. Scribd

Your intuition that "higher number = more filtering with greater lag" is actually backwards — it's a counterintuitive parameter. Higher number = faster response (less lag), lower number = slower filter (more lag = more AE). The forum thread has it right

 

There seems to be some confusion in this thread because the documentation and the forum comments are describing two very different parts of the AE chain. When you separate those, everything lines up cleanly. The documentation is referring to how the ECM uses the filtered TPS to calculate the magnitude and duration of TPS‑based AE. A smaller coefficient creates more lag, more lag means the filtered TPS moves slower, a slower filtered TPS produces a smaller delta TPS, and a smaller delta TPS results in weaker AE and shorter AE duration. That part of the documentation is absolutely correct. When tuners say “lower the filter to make AE come in sooner,” they’re talking about AE enable timing, not AE magnitude. AE enable is influenced by the difference between the raw TPS (which moves instantly) and the filtered TPS (which lags depending on the coefficient). When the filter is slower, the raw TPS jumps, the filtered TPS lags, the difference between them grows, and that difference crosses the AE enable threshold earlier. So AE can start sooner, even though the AE pulse itself is smaller and shorter. Sounds a tad contradictory yes, but only if you assume the same TPS value is used for both AE enable and AE magnitude, but GM doesn’t do that, and the EBL is fundamentally GM code with patches layered on top. AE enable is influenced by the difference between raw and filtered TPS, while AE magnitude and duration are based on the filtered TPS delta...

- Rob

 

Thanks Rob for chiming in on this. You know this probably better than anybody on here. You always give great advice. Also, can you contact me when you get the time? Thanks.

 

Hi,

I was wondering if someone could help me find the cause of the idle issue I have been having. The back story is my ignition coil went bad and fried my ICM while going highway speeds after it warmed up. Huge backfire out the exhaust and stalled. I have since replaced everything ignition related: Plugs, Wires, Full distributor assembly, Coil, GM ICM, did the full tune up. After I got it running and set the base timing back to zero everything seemed fine until the next morning. Basically, what is happening now is my idle is jumping around erratically for the first minute or two but only after the truck sits for long periods. I live in the north, so I have seen this in -30C and now it's still happening in +20C but only if it sits for around 6 hours temperature does not seem to matter. Engine seems to run decent as soon as this surging stops. I might have a slight surge after it warms up but nothing crazy. I believe that this problem is more tune related but I don't know where or why this started after doing the tune up. I am sure the base timing is set properly.

Engine is a TBI 350 running the EBL Flash II. I have a VRFPR set at 18 psi. I have also tried putting the fuel system back to stock at 13 psi with the stock regulator and that made no difference.

I have attached a log of this happening. As well as the current tune I am running. Does anyone have any idea?

 

You replaced the distributor? With aftermarket HEI? ICM's need to be stock GM units, using the same p/n you originally tuned the engine with.

Not sure that is your problem, but a place to start.

 

Yes, replaced the distributor. I just picked one up from the local parts store some cheap WIKA brand (thats all they had). I did some reading after this first started and replaced the ICM module in the new distributor with a GM genuine D1943A. I also changed the magnetic pickup just in case it has a crack or something. Basically rebuild the new distributor with GM parts just in case the components were cheap junk.

I am realy lost on what to try next other then messing with the tune. Both the Whats up display and tach in my truck show the rpm jumping around like that. But after a minute or two it smooths right out.

 

That is definitely weird. Doesn't seem tune related because your IAC isn't moving. Not to mention it is an abrupt change from 800ish rpm to 2000s and back to 800s within 3/16th of a second. Not even sure that is physically possible. Whatever is causing it, it is contributing to the SA and the DC going all over the place each time it blips.

 

Yes, it's very strange. The EBL must be picking up some kind of strange signal from this cheap distributor. I can say that the EBL shows much higher spikes in RPM then in reality, I am sure it's because the computer can read these signals much faster then my tach. Usually my tach shows this bounce around from 800 to 1500 rpm never actually seen the spikes to 2400.

I'll order an AC Delco or GM distributor and hopefully everything goes back to running normally. I appreciate the responses, I have been loading the parts cannon and chasing my tail with trying to tune this out. I'll send an update once the distributor gets installed.