I called the guy who I bought it from today and he wasnt very clear but it sounds like the 86s had valve shrouds on them for better emissions that was taken off in 87. These shrouds are what caused the poor air flow but also increased low end torque but it wasnt as good as the 87s at high rpms. It sounds like my internals are all 87 and its just my heads that are 86. It is also possible that the valve shrouds are not on which pretty much makes these 87 heads just with the deeper threads for the spark plugs which is actually benneficial. I dont think it will be worth the hassle to get the 87s. These heads might actually be better then them anyway.