Thread: car running lean

I recently had a exhaust leak on my gtir motor so i decided to fix the problem which ended up being a blown out exhaust gasket, well after i got the new gasket and mani back on i started to car and its running super lean. My wideband is leaner than 17.0 at idle and runs so bad it wont even hold an idle. If i hold the throttle around 3000 rpms the car just revs up and then revs down then revs up and revs back down the idle wont stay constant. i checked everything i can think of so any ideas out there id be happy to hear them thanks oh and car ran fine minus exhaust leak before