I have a 2004 Nissan 350z and I just recently changed the spark plugs because the check engine light came on for a misfire in cylinder 1 and a random misfire. I changed all the spark plugs and now my car won’t accelerate past 1500 rpms at full throttle. I read on other forums that the fuel pump might be out and I’m starting to think that might be it because the past owner used regular gas. Also my fuel gauge fluctuates at times. What could be the problem?

 

check for air leaks