Originally Posted by RWC

The same intake manifold assy is used on the 06 and 07 Trailblazer LS2, the new 4.8L, 5.3L and is a good improvement over the older truck manifold. The new 6.0L and 6.2L use a different manifold. I have not measured the new 4.8L 4 bolt TB yet but it shares the same intake as the 5.3L and should be the same TB. The 5.3, 6.0L and the 6.2L in the trucks use the same 87mm TB (measured across the blade along the shaft), including the TB LS2. I don't think they would need to have a different one just for the 4.8L. The car LS2 - LS7 TB measures 90mm. The "new" manifold assy seems to flow reasonably well when you look at what has been done with the modded LS2 Trailblazers using this same setup.

Originally Posted by L33Z71

Thanks for the confirmation. I had heard/read that the Gen IV truck TB's were 87 MM but wasn't sure because of the source.

I would be interested to know if the 90 MM TB would bolt up and plug and play as a swap. I'm sure tuning would be required, but could be a nice alternative porting.

Originally Posted by RWC

I went back and looked at some old posts and it seems to be a plug and play on the TBSS and SSR with maybe some tuning needed. No info found about it working on the new 07 4.8L, but it probably would. The swap results sounded good, but you might want to do a search for "90mm" and read up some more on it for yourself to come to your own conclusions. I might try this on my 6.2L if I have time. Hope this helps.

Ron