Two days ago it started sputtering and surging under load. At idle it was fine, but under load off idle, it was like a carbed motor with the choke set. Here's what we've done:

plugs and wires are nearly new
cap and rotor are nearly new
new ignition coil
new MAP sensor
new fuel filter
idle air control motor looks good
injectors are clean and spraying plenty of fuel
fuel pressure appears good
did a tap test on the computer and that was fine

I'm running out of ideas now. Any thoughts on what else we could try? Can't wait to get the LS1 swap done.

 

I would check the timing and replace the fule filter. Both can cause the symptoms you describe.

 

CTS?

 

Could be but I would start at the fuel filter anyways. That most likely needs to be changed.

 

check ur vacuum plugs

 

do you have a cat on it? a clogged cat will cause that. and if you have been running rich for a while, that will kill a cat in a hurry.

 

Fuel filter has been done, and the exhaust is catless. What's a CTS? Crank trigger?

 

Coolant temp sensor

 

Did you check your base timing? I would also check the cat like Dewey mentioned. Run the car for awhile and pull it into a dark garage. Pear under and see if it is glowing red.

 

There still is no cat on the car. I think we've got it traced back to the computer, so I'll rip it's guts out and replace it. I've checked everything else and there just isn't that much **** that can go wrong on a TBI engine. Blah. I need to hurry up and find an LS1 block.

 

what does it mean when it glows red and what could it be

Fixed your quote for ya.

 

When it glows red it is running vary vary hot and is not working properly because it is clogged and is backed up. It becomes a heat sink and acts like a furnace.