Needs some input here. I installed my greddy turbo kit with a bnr stage 2 upgrade a week ago and ran it on the base tune from MM till our scheduled tune day yesterday. During my WOT pull in 3rd gear I reached about 6-7k with AFR in the 12’s and about 6-7lbs of boost when suddenly the motor sputtered and began to run really rough. Thought at first I blew the motor but as me and Jeff(MM) started running through it the motor was fine. Still starts up right away but just won’t idle correctly and is extremely choppy through the rev range. AFR now is running lean +17 whenever I give it to much gas. I was able to limp home at 2-3k maintaining 14.7afr. Today I found 2 of my spark plugs fouled and replaced them and now at least I’m able to run a rough idle and not have the car die out. I’ve checked all my couplers and everything is on tight. However when I unplugged the maf and gave it gas I couldn’t build boost. I unplugged the maf since by doing so I was able to keep my afr normal and not go lean. Does anyone have any idea where I should start looking next to solve this?

 

Check all the vacuum lines/hoses to make sure something didn't pop off. Make sure everything is clamped/tied so nothing comes loose either. Do you have another front O2 sensor and MAF sensor that you could swap in to the car to eliminate those as failure points as well? Also make sure you aren't getting any unmetered air into the system after the MAF before the turbo.

 

You need to leak test your system ..... search 'boost leak test , mighty car mods ' . But be aware that you may need to block your vac hoses and that your turbo will leak air into the sump.

 

^^ Those suggestions seem more likely, but maybe the fuel pump or possibly injectors too. Because you provided no history of what you had before when the kit was installed. A proper turbo installation should also include fully refurbishing both the fuel and ignition systems too, but as we’ve often seen here, a lot of people fail on not doing this.