Just got my 2008 G37S about a month ago. It came with a Beluga Racing Axle-back on it. So far I have deleted the resonators, and installed test pipes. The car ran awesome for about a week, then I installed a brand new Stillen G3 Intake. Drove the car around the block and came back home. When I tried driving again after letting the car sit for about an hour it did fine for about .5 a mile. Then it started acting up. It was really rough with the gear changes (its a 5at) and there was little throttle response at all. It almost sounded like I had installed some crazy cam, and on top of that, in between shifts it would backfire. I took off the negative connector to the battery and let it sit overnight. When I turned the car back on it wont even idle any more (idles for max 20 seconds then dies). The g/s through the MAF is around 7 (cant find what the average g/s is for our cars). It isnt throwing any CEL. I'm not sure what is the problem at this point in time. I've called Stillen and they are telling me it is a vacuum leak. I have checked all the hoses probably upwards of 5 times now, and I can confidently say, everything is connected and tightened properly. Does anyone know what the problem could be, or has anyone had a similar problem? I'm bringing home a computer to relearn the idle tonight, and hope it gets better. Any info is appreciated. I can post a video if it helps.

 

Are the mafs inserted the right direction and securely to the connectors? If all that is right its simple enough to take off the engine bay side of the intake and reinstall by the numbers. As an afterthought did you pull the mafs and make sure you didnt get crap on them? Last time this happened to me I was rushing an install and forgot to plug the maf connection.

 

Both MAFs are plugged in and on the right side/direction. I got 2 new MAFs that should be here tomorrow morning. Gotta love warranty. Hopefully that fixes the problem. If not it's back to the drawing board.

 

Try cleaning the filters (if it's used) and your throttle bodies. May not be the solution but it may help.