What exactly happens when you change from open loop to closed loop? I've changed almost all of the sensors, put the manifold on three times, and still can't find why my car runs like chit when it transfers into closed loop. I've changed the MAF, TPS, ECT, IAT, Computer, both O2 sensors. I've redone the manifold three times because I thought the problem was that the manifold was leaking through the gaskets. I can't find out what is wrong. It loses power when I give it any gas sometimes when it's in closed loop. If I turn the car off and back on, the problem ceases until the car goes back into close loop. The timing is at 10* and I have a tweecer so the temps are all set down. I'm outta ideas.