I'm out of Ideas guys. I have put shorty headers with a welded in 02 boss, dynomax exhaust, and a new throttle body on my car in the last 9 months. When I take off it feels like the car almost dies because the excess fuel. I just changed the 02 sensor, so I know it's not that. If anyone has had this problem or has an Idea please help me out. Thanks

 

I had a similar problem on an Iron Duke four-holer with a TBI. It turned out that the fuel pressure was LOW, not high. I was confused until I understood that th eECM was trying to correct for the lean condition in incremental steps, and the final "step" was a huge one that made it way rich.

That may not be your problem, but it might be a good idea to test the fuel pressure. And as long as the fuel pressure gauge is connected, shut down the engine and see how long the system holds pressure. You may have leaking injectors or very poor spray patterns (streamers) that are making the manifold way too wet.

EDIT: Another thing to check on a TBI or S/D setup is the MAP sensor. A high reading (low indicated vacuum) can cause the ECM to adjust to a very rich mixture.



Make sure the electrical connector is clean and tight, and that the vacuum hose to the MAP is intact and connected. You can test the MAP oputput voltage at a known vacuum level and conmpare it to the chart:

 

I should have added a few more things to my post. when I first accelerate it is very boggy, but when I hit a certain RPM it acts like it leans out and runs right. My tack has also stopped working, and I found a broken hose? made out of hard plastic toward the back pssenger side of the engine. It is broke right at a t in the line, and I'm not real sure what it's from.



thanks for the info so far vader

 

I have a 305 TBI, and I think that T-fitting is for EGR I think. Yeah those stock plastic lines break real easy, mine have all been replaced with rubber lines. But, one more thing to consider, is, is it throwing any codes or anything, if it is the ECU could be dropping into open loop mode, which makes the car run pretty darn lean, but then again, it doesnt perform in the upper RPMS, Im confused.