NOS fuel addiditive

[84_GT350]

Is this stuff just for EFI cars or what? I put some in my car and it seems to be running like @ss. Sometimes it's like it's about to just die at stop signs, when idling, etc. The only other problems I know of are (what I believe to be) a bad valve cover gasket (it smokes real bad from under the hood and one of the header primaries is black next to the head) and a bad PCV valve. But the car ran so-so until the NOS stuff. I used the off-road stuff with some 91 octane gas. WTF is going on here?

------------------
1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s