Time for a new clutch?
 

Hey everyone how's it going,

I recently bought a BAMA tuner for my 03 GT and had my car tuned for 91 octane fuel. My car runs great now and the throttle response has improved tremendously! That's not the problem. The problem is now when I go to the red line I can hear the clutch making a weird noise. It's all like, "GKGKGKGKGKGKGK" and I'm all like, "Clutch no!". But yeah basically what happens. To test my theory I got my car to 40 mph, and put it in 5th. Pressed the accelerator pedal and much to my dismay my car would not increase in speed. I fear I need a new clutch. Any help at all would be greatly appreciated. Thank you!

When you did the 40mph/5th gear test did engine speed increase? Just because the car didn't accelerate doesn't necessarily mean anything, especially if you have stock rearend gears.

Not sure what to say about your sound, diagnosing that sort of stuff over the internet ain't my thing. Hard enough sometimes when you're standing right there...

The engine speed did not increase, also at idle I will hear a faint noise, which goes away when I push the clutch pedal.

I doubt that my stock GT will pull very hard in 5th at 40mph,and your tune may have affected how yours pulls at low rpm..
Your faint noise is probably the throw out bearing.Probably nothing to worry about.The red line noise is something for concern.
I'd initially judge a clutch plate by slippage in first.

Good to know. How do you test slippage in first?

If you hit the gas in first,and the rpms flare up,and you're not spinning your tires or accelerating like you should,the clutch is slipping.
A 2001.15 years old.-we don't know the mileage,perhaps you don't know the repair or driving history.It could well be time for a new clutch and pressure plate.It you go in,you replace everything that's clutch related.

So I tested the slippage in first, there's no slippage. But I figured out a better description of the sound thanks to my lovely passenger. I put it in second gear and went from a stop. She described it as a "shopping cart going over the bumps in a parking lot". Pretty accurate now that I think about it. The sound only occurs at low rpms at WOT. Any thoughts?

Also a little more about my car:

2003 Mustang GT, 73k miles, aftermarket CAI, 70mm TB, Plenum, Magnaflow catback exhaust, BAMA racing tune.