86-91 swap
 

I just bought a 1991 13b to put in my 1986 rx7, what difficulties am I in for? Is the ecu going to be a problem?

i think your better of finding the ecu and wiring harnest because the 86 fc is weird man... i had one and the wiring didnt match to certain things in the s5 n/a motor... you can make it work but where i ran into problems was in the m.a.f sensor and ecu... it wouldent fire.. finally i just bought the wiring and ecu in the junk yard and it fired right up...