Car runs really bad in closed loop, please help
Car runs really bad in closed loop, please help I have a 98 z28 m6 with headers and an air lid, my car misfires very bad when the car is in closed loop, when i first start it up it will run perfect for about the first mile and it will go to misfiring very bad. if i push the gas pedal to the floor it will instantly clear up but will return to misfiring at any point except wot. It will got back to running perfect as soon as the car enters open loop, I have codes for the front 02 sensors not switching fast enough (insuficent switching), i have the rear corvette 02 sensors installed in the upstream postitions and have replaced them with no change. when it goes to misfiring the LT and St trim will go way negative? i have seen it at -40... i took it to a respected tuner and he cleaned the maf sensor, it ran perfect on the dyno but started misfiring again about two weeks later. it made 334 hp on the dyno, which i was very happy with. i have cleaned the maf again and even replaced it with no change... can anyone help with this problem!!!!!! 
If it only does it in closed loop, then it is most likely the front o2 sensors since in closed loop, they are looking at the o2's for fueling feedback, especially if you got the trouble codes for insufficient switching. Check your connections on the o2 sensors, and do a full scan to see if they are heating properly. You've got an o2 sensor issue somewhere. It clears up when you go WOT because it then ignores the o2 sensors and refers back to your maf/map sensors and your VE table/PE table for fueling requirements.
