My engine has code P0300 after replacing both valve covers/ gaskets and a plenum spacer. I drove the car normally for 1 day, the next day the car would lose power over 3k rpms and it’s running lean, I noticed that the STFT in bank 1 is 25% at idle and bank 2 is around 15% while the LTFT is around 5-9%. Whenever I rev the car the STFT and LTFT seem to go down significantly. I have checked for vacuum leaks using a smoke machine and found none, I have double checked my gaskets and already replaced lots of my pcv hoses. I did a throttle body relearn and ran sea foam through the injectors. Spark plugs are only 1000 miles old, not to sure how old the injectors or coil packs are. My upstream 02s seem to fluctuate normally but my downstream both seem to be stuck at .270-.280 volts. MAF has normal lbs/ min. When I crank up the car it starts up very low rpms like it’s about to die then shoots up to 1-1.5k. It’s run very bad and has bad fumes from running lean. Any suggestions before I replace injectors/coils 2003 g35 sedan 6mt

 

Did you do the idle air recalibration steps listed in the FSM?

Section EC - Engine Controls under "basic service procedures".

https://www.nicoclub.com/infiniti-service-manuals