Just became a new member to this site, so forgive me beforehand if this question has already been answered. I haven't yet figured out how to really navigate through here.

I have a manual 2011 mustang gt that's basically stock minus the exhaust. I recently encountered the problem that when I really get on it the car accelerates, but nowhere near the same as it used to and the RPMs rev up really high. About a few days before that (believe it was before anyways) I got a check engine light, took it into autozone and had them read the code and came back low coolant level or thermostat needed to be changed out. Had the thermostat changed out and obviously filled coolant. As far as the acceleration problem, I figured it could have been the clutch slipping and or transmission fluid needed changing. Had fluid changed (didn't fix it) and then also bought a new flywheel and upgraded the clutch (planning on putting in a supercharger anyways). Had that installed and I've been trying to drive it calmly for the "break-in" period, but today I decided to get on it...and once again poor acceleration. Doesn't have any problems accelerating unless I really get on it though. Really hoping it's not the transmission itself. Any inputs would be greatly appreciated!

 

Also, checked engine light seemed to be cleared, but when I got on it earlier it came back on. Not sure how the two issues are related, if they even are.

 

If the rpms are high and the car is slow to accelerate, is usually a slipping clutch.

 

Just for the sake of checking things out,,, Turn off your traction control.

 

Tried that as well, no change. Wondering if it could be something in the differential. Also now having other problems. Check engine light had cleared a few days ago but it was coming in when I really got on it every once in awhile. I thought it was related to coolant temp again but now it's throwing up codes P0300, 345, and 349. All seem to indicate cam shaft position sensor but I guess it could be a number of things. Cars seems to now hesitate at times.