Well just got my engine in from mazda racing.Anywayz i had a 87 t2 and in went on me. So i ordered a 91 j spec what do i need what can i lose and no i dont care about emmissions

 

wHAT THROTTLE BODY MOD?????

 

you can remove everything that isn't needed to squirt fuel into the engine or control the ignition timing, everything can go south.

I have a haltech E6K controlling my show, and i now have nothing left in the engine or on the engine which isn't involved in running the engine itself, I have NO valves etc on either of the intake manifolds, everything has been removed. including the BAC.
on the TB, you can remove the coolant lines and the front set of secondary butterflies, if you get keen you can also smooth out all the ridges in your TB while your at it.

The OMP can be removed, and the place where it was can be blocked off with some 1.5mm aluminium and some silicone sealant.

just put a bolt into the holes where the oil injectors were in the housings and the lower intake manifold and now you can just run premix, which is soo much better on ya engine, it now means you can run fully synthetic engine oil and not worry about it gunking up your rotors.

 

Im not sure what your plans are but when i bought my JSPEC motor (91) to be put in my 87 TII i was told to remove some stuff off the old motor and swap it in JSPEC. This are some things that i can remember that needs to be in your 91 jspec block:
FRONT COVER-- so you can use your mechanical OIL METRING PUMP.89-91 has the electrical OMP
LOWER/UPPER and TB
RAILS AND INJECTORS
SENSORS
WATER PUMP HOUSING+ WATER PUMP
hmmm other than that i think that's it!..but PLS USE THE 89-91 TURBO+ MANIFOLD!.

So to make a long story short all you need is your 91 block and the more superior turbo and manifold.
GOOD LUCK!
PS Dont forget to buy new gaskets for your intakes and probably for the front cover.