This code popped up after a week from putting on my 3 piece intake spacers I highly doubt it's a leak though I know most of the time this code I hear is from a bad spark plug or coil pack but mine were just replaced 7k miles ago with ngk plugs and coils I cleared the light then 70miles later the same code came on again and also a p0174 code bank 2 system to lean so is it a sensor? I replaced the bank 1 sensor 1 recently with the Oem bosche sensor I know that's a completely different bank could it be the man sensor? I just don't want to spend money on the wrong stuff

 

I would suspect a leak since both codes popped up AFTER you installed the spacers.

 

Yea just gotta find out where its coming from

 

code P0300 usually says multiplies misfires, but since you don't have specific misfire code for what cylinder, so it's a vacuum leak, where you mention you put a three piece pipe, you have a intake leak, so you need to get carb cleaner and spray it on the piping while the engine is running and see where it sucking that's where your vacuum leak is at. it can be anywhere from a small leak to a gross leak