I am running full open loop, '165 ECM. Major mods to a HSR 383. Tune is really good when car is warm and has been shut off and restarted. WOT AFR's hang right around 12.2 to 12.7. Part throttle AFR's range from 13.8 to 15.2. All is well. But.... When I first start the car and warm it up, or when I restart it after it has sat for an hour or so, the AFR's stay about 2 full points too rich as seen on the wideband. Even if I let it run and drive it for an hour, the AFR's will stay way rich. It isn't a false reading, it will pop out the exhaust at WOT and plugs are BLACK if I drive it this way for quite a while. It is way rich during part throttle and WOT. So I pull over, shut car off, restart it, and the AFR's are then perfect. And they will stay fine no matter how long I drive or how many times I shut off and restart the car. Popping out exhaust is gone, wideband reads good, plug readings look good. Unless it sits long enough to cool down, then it will be rich again until I shut it off and restart it. I've tried alot of things, different AFPR, relocated MAT to air intake tract, messed with a few things in the tune, etc. What could be causing this? It's almost like there is a setting in the tune that tells it to keep it rich after a cold or cool start and don't let it lean out, then it resets on a hot restart. I haven't messed with any of the CCP settings in the tune, could that be causing this?

Have you messed with cranking and startup fueling? Startup Enrich Decay Delay vs Coolant looks like it might be a place to start.

Thought I should update this. After nearly 1.5 years of having this issue and about 200 tune re-burns, I think I found the solution. I could never get the afr's right at part throttle, they were always rich when driven for the first 1/2 hour or so, then got leaner and leaner the more I drove after that, especially in town or after I shut the car off for a few mins then restarted. I drove the car yesterday for a long time, and it got lean. Stopped and filled the fuel tank, and it was back to rich. Was running at like 12.5 part throttle, through the day leaned out to like 17 afr at very light throttle. Filled the tank, went right back to 12.5. I changed the tune to get it back to about 13.5 (where I like to run), ran it, and all was fine. Burnt up about 1/2 tank driving around all afternoon, afr crept back to the 17 area. Stopped at a gas station and touched the gas tank and WOW! It gets hot! Filled the tank back up and and bam, back to 13.5 on the wideband.

I'm sure now the fuel is getting too hot. I've chased this forever and went crazy trying to find the problem. I have rerouted fuel lines so they are away from the headers and not on top of the intake and changed the AFPR at the same time, and the issue got a little better but not much. Figured the change was due to the new and improved regulator, never thought it was the fuel not getting as hot. Now I know.

Sorry about the long post, but the underhood temps on a high compression, headered, 383 (with an hsr intake in my case) in these cars is crazy hot, as we all know, but I now see that it is so hot that when running a high volume fuel pump it is circulating the fuel very quickly over the engine. It gets much hotter than expected. If anyone reading this has a good or rich running car then after an hour or so of driving a lean condition or what feels like a lean stumble or anything of a lean nature pops it's head, look into your fuel temps before doing anything else!