Hi guys I have a evo iv which I bought a few days ago, running a evo 7 ecu flash tune
My friend took the car for a drive and came back with the car running like a dog. Car is like on limp mode

For the last 2 days I have done everything I could think of, spark plugs, coils, boost leak, iacv and throttle body.
Found also that the hks mushroom filter was deteriorating so I had installed anew.

When I did all the above and started the car it ran/idled correctly for about a minute and the car went back to limp - idle was rough and sounds like it is misfiring.

I'm backtracking what I have done but I have put in a different gas to what it was tuned for before the friend went on that drive. I'm wondering could fuel/bad fuel cause these issues?

Any inputs would be much appreciated. Cheers

 

Maybe your MAF went bad or is going bad. check for boost leaks? IC piping couplers popped off?