86 mustang GT 5.0 mass air flow

Are you running a bigger cam? A bigger mass air will help the engine breath a little more but without a bigger cam to let the air in your just wasting your time. I'd suggest at least a motorsport e303, 24 lb. Injectors, and a C&L mass air. You want you air meter 4 mm bigger than your throttle body. Good luck.

86-88 are speed density (except 88 california) they did not go MAF until 89 model year. So unless you upgraded your speed density wiring to a MAF style then it doesn't matter. 86 also had e6 heads and 87-95 had e7 heads. You would be much better going with gt40(p) heads at minimum for cast iron or upgrade to aluminum heads for best gains. 86 also had flat top pistons, so a head swap may cause issues with valve to piston clearance. Especially if you go with a bigger cam. Good luck