How can you tell the difference between an NA and TT upper plenum if the TT badges were taken off from the TT Plenum. I saw 3 upper plenums from the local wrecking yard today and I can't tell which one is which. How about the lower plenums are they all the same TT & NA.

 

I believe TT and A p[lenus are the same. but year differs. for some reason a 94 plenum wont fit a 90 motor. but TT and NA are same plenums

 

Bardabe is right. The upper plenums are all the same from 1990-2000 i believe. But the lower plenums are what changed i think. They are machined a bit differenly

 

That this means I can use the upper plenum of 90-96 N/A on a 90 TT Lower Plenum???

 

Upper plenums are interchangeable. Lower plenums are a different story depending on what year due to different injector types.

 

Thanks man!! I guess I'll be buying the upper Plenums soon. I am planning on getting the lower and upper plenum polish and ported. What power gains shuold I expect on the ported and polish Plenums? What year did they change the Lower Plenum size 90-96??

 

10hp tops, depending on the other modifications you have.

 

I got a 90 upper plenum up for grabs. I was gonna paint it but running out of time.

 

Yes, will work fine. They are the same.