you should yes..I did the 87 ECM conversion to my car and put on an 87 MAF....after I saw that it was running fine I put my 84 MAF, and it kinda put out a blackish smoke when I reved the engine.
yes you also need it and also the mat senser aka incoming air temp and mat plug got mine at the local gm dealer 39.00 for mat and 20.00 for plug then go to gnttype and it will tell you where to hook it up to the 86-87 ecm
