I have a 02 Trans AM with NGK TR55 set the gap at .50 she ran to rich and then set the gap to .40 started to misfire gave me check engine light both times when set to .40 gap got P0300 and when set to .50 got like 3 codes P0140,P1133,P0160 Just wondering where the gap should be set at. It have bolt ons Header, Exhaust, Air lid, KN filter Stall 2800 342 gears

 

Check the O2 wiring...
At .040 should not be the problem....
Other codes are all sensor related, including heaters. Could be the Lt's are causing problems w/ getting the sensors hot enuf to work...