I recently put spacers the large nwpthrottlle body and headers on my 2005 nissan maxima i obviously have air fuel/ratio sensor codes but I'm also getting a random misfire code p0300. any tips i haven't had it tuned yet.the exhaust wreaks of fuel.also all cats are deleted

 

Sounds like an intake leak which can cause a misfire. That or use a timing light and place the inductive pick up around each coil pack pigtail and you can see which cylinder is missing watch the timing light impulses. Once you find the cylinder that is the issue swap around it's coil pack and see if the problem transfers.