First let me say thank you for allowing me to join this forum. I have a 87 trans am gta with a 5.7. My mechanic was fixing some vacuum leaks and did a smoke test and seen smoke coming from the back of the throttle body leaking from the gasket. I need to see if someone can identify this throttle body by the part number 17086051 0066 JPA. The data plate on top has TPIS. I also have attached 2 pictures one of the top and the side with the part number.

 

Stock is 48mm if pull the inlet and picture the bore blades bored out tb is 52mm Efi connection has the gaskets needed.

 

Looks like a 85-88 throttle body, most all aftermarket gaskets will work for this even if it's modified with a larger bore.

 

^^Correct. If there is a little overlap it won't be a major issue. While a popular aftermarket "performance" item for a while, the bored throttle bodies were later proven to be useless for a regular TPI, just as had been explained and posted here over 20 years ago. The GMPP RamJet 502 crate engine (12499121) originally came equipped with a 48mm stock throttle body. It made over 500HP and 565 ft/lb on that. For those who ignored the physics, the results on the dyno may have resolved the question, even if the science was beyond their comprehension. The oversized throttle bodies probably did make some people happy that they thought they "fixed" a non-existent problem, and certainly made people happy when they sold them to that former group.