not really limp mode? help! cars sounds different now

[STONYEVANS]

i ran my bone stock sstc 09 cobalt with 4000mi to hard maybe...the car went into some mode after high rpm from 1st to 2nd and back to 1st..the exhaust and turbo got quite.. after research i found it could be in limp mode...i reset the comp and a quick massage appeared on the display saying there was a problem..i couldn't fully read it because it was a lighting flash massage..anyway...the car started and it sounded like it did when i first got it, crisp exhaust noise and turbo felt great and it pulled like new..I KNOW NOTHING ABOUT THESE CARS...bare with me...thought i was good to go..the next day and the more i drive it the car its not crisp sounding and the turbo pull is OK...just not running like it did before but it runs great..140 mph the other day. help..

 

[YelloEye]

It happens, welcome to crappy GM tuning. Mine decides to limp if I WOT shift 1-2 and get the timing just wrong.