which MAF? 73mm, 76mm, 80mm??

Josh, weld-in subframes are a must on every stang (that's a given). But, to answer your question, yes, you need to upgrade your MAF to a 75 now. Your stock MAF isn't sucking enough air to feed that TB or TFS intake.

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'90 LX 5.0; 12K original miles (no sh*&); 3.55 gears; pulleys;Edelbrock Performer Heads; BBK shorties; MSD 6AL box w/ blaster 2 coil; Motorsport E303 cam; Pro-M 75mm MAF; BBK 70mm TB; Eibach spring kit; Southside welded subs; K&N cone filter charger; Hurst shifter; fiberglass turbo hood; A/C-less; rear seat-less; cat-less; 2 chamber Flos; Corbeau racing seats (fronts);
30# injectors; JMS Chip; 190 lb fp; TFS track heat Intake (12.299 @ 113)