Alright well first i wanna say i have an 03 saleen Supercharged.
I bought it used. It has aftermarket pulley, jlt intake, 42lb fuel injectors, idler pulley and exhaust.
Ok so i have no idea if it has been tuned. but i would assume it has after all that stuff.

But i have some issues. I get a surging/stutter between 1500-200rpm when trying to keep a steady speed/letting off of acceleration. I also have a semi rough idle. its drops up and down.

With the Ac on the idle problem goes away but i assume that's because of the rpm being a little higher.

I had a similar stutter problem in my 02 focus years back. It threw a code and i found it was the MAF sensor. I want to check the MAF on my stang but havent had time as its in the fender well.

Any suggestions?

I also found the other day that the IAC plastic box thing was no clamped adequately and was kinda coming off. I re-clamped it but no change

 

I had the same exact rough idle and 1,500 - 2,000 surge issue with my Vortech supercharger and the stock MAF, I put a different MAF and intake tube on it and the problem went away.