So, I have my TPI more or less tuned.

• Runs great in what I believe is open loop (cold or WOT conditions).
• Runs a bit rough in closed loop- seems to have a bit of a drop in power and a noticeably different sound to the way it runs. Almost like a light miss.

Does this only when warm... usually after about 20 minutes. No check engine light. No codes.

Base timing is 10 degrees on a GMPP 12499529 engine with a heated O2 sensor, 1.6 rockers, SLP runners and 24lb injectors.

Thoughts?

Engine has less than 2k miles on it, injectors were replaced almost at the same time.

 

You may be running a bit lean.
Do you have access to a scan tool?

 

That is what I'm thinking.

Not yet. I need to purchase an ALDL to USB. I have another chip. I think I'll swap it and see what happens in the meantime.

Thanks for the reply