[TLS2000]

The 3900 (LZ9) is a different block from the 3500 (LX9) in the G6. It shares parts with the 3500 (LZ4, LZE) in the Monte Carlo and Impala. The LZ4, LZE and LZ9 are completely new 60 degree v6's with VVT.

The 3500 (LX9) in the G6 V6 and GT is based off of the old 3400 in the Grand Am / 3100 in the Malibu. These engines do not have VVT.

So the RSM supercharger for the 3500 (LX9) will not work on the 3900 (LZ9) or the 3500 (LZ4 or LZE).

 

[TLS2000]

It's actually GM that's messing you up. It's not obvious that they have 3 different engines called 3500.

I only found out that they were different when I went to the GM Powertrain website and read up about them.

edit: At the same time, if RSM wants to use my car as a guinea pig for a supercharger, they can.