I have a 1990 stock 5.0 with AT. Any advice on upgrading to a CAI, bigger MAF, bigger TB and EGR spacer? Do you get any significant gains from the any of it or is it just a waste unless you do bigger upgrades?
Wow, how do you answer that question.
you likely won't notice anything. And when you start miss matching parts you will go backwards in the performance department.
plan you build around how you are going to use the car. A gear change would be a better dollar spent with a stock engine. Then plan a head, cam and intake change.
JMO
Doubt you'd notice much really. The stock MAF is probably a restriction so going larger here may help, but not in any significant way if you have stock intake manifold and heads.
With the AOD, i'd recommend 3.73's or 4.10's over the mods you listed. Add a trans cooler and if you can swing it...a shift kit and a bigger stall converter.
The engine mods you listed would work well if you changed out the intake manifold and heads. If you aren' going to change the heads anytime soon, pick up an explorer intake setup off an early 96/97 explorer. You can convert the early 65mm TB to work on a Fox. Can probably pick up the entire setup (intake, TB and 19# injectors) for $100 or less from a boneyard. The injectors offer a better spray pattern than the old fox 19's.
If you do decide to do heads, which head you pick may dictate a "better" intake.