OK so I had gscS2 cams installed last week on my car and a dyno tune, The car ran fine when I got it back, had a ton of power and pulled hard. 3-4 days ago it begin cutting out at higher rpms under load, I pulled my plugs and they were awful... so reinstalled plugs today gapped them to .25 and it seemed to help somewhat, so my next guess was maybe a gas station around here sold 87 as 93 so I mixed a little 110 in it to bring the octane up, this too helped a tad, or seemed to. Now the only time it seems to cut out is between 4-5k rpms and after that it begins pulled hard, It surges and backfires hard at these Rpms, and is a moderate pop in 1-3 gears and a bucking and popcorn sound in 4-5gears. I am starting to think it could be the tune, but it ran fine just a few days ago, it was almost near perfect. Im completely confused because the more I drive with the new fuel it begins to somewhat clear up , and next pull it will be bad again.

 

I'm assuming you've already checked for boost/vac leaks. Correct?

 

I had a somewhat similar issue BEFORE my tune. Was just the fuel cut kicking in while around 5k + RPM. Around the same time swapped in a walbro 255 and and got the car tuned which fixed the problem 100%

 

Car has a walbro already installed, it just randomly started running this way, gonna try gapping to .20 and see if it helps... checked all my connections on my piping they are all snug, havent jacked up the car to check the hot side piping, maybe its leaking there. No vaccuum leaks though.

 

+1 on boost leak test. What are you using for boost control? Do you have a way to check for overboosting?

 

Who tuned your car?

 

The problem is almost resolved I regapped my plugs and now it just barely hesitates in 4th only when punching from 4k, the bucking has stopped, I'm starting to think one of these mom and pops stores around here is selling bad gas.... Because the more I drive it the better its getting or maybe its a combo of the plugs too, who knows... and Top speed Motorsports in Atlanta did my tuning, as I said the tune was fine for a few days ran really really well, then just fell off 3-4 days ago with the surging. Even more reason to think I had bad gas, Because for a week solid the car pulled hard and drove better than it ever has.

 

I'm also stock boost controller, I haven't gotten to that road yet. I need to run a test just to check for leaks, but I just got back out of my shop crawled all under it and double checked my worm gear clamps and they are tight as can be, all the connections are made up tight and snug, I really don't see how it could be leaking but I also said that about my SRT-4.

 

Change them to all t-bolt clamps. get a 3-port boost solenoid and retune. it might be better.