I have been talking with Mike about his TB's, here is what he recommends:
"You pretty much need to stick with the LS2 as the base programming in the VCM is set for it. The LS2 and LS3 are both 90mm units, just a different body configuration due to a new supplier to GM in 2009.
The LS3 style does flow more then the LS2 when they are STOCK, but the CNC work pretty much equalizes them."
So, looks like stock for stock, the LS3 will flow more than the LS2, but once is all said and done with the port work, sounds like they will flow right on par with each other. Also, sounds like to tuning will be needed with the LS2 version over the LS3.
'14 SS MYSTIC GREEN 1 OF 11 OPTIONED- KOOKS, VCM, EIBACH, VMAX, CTS-V WHEELS, PAT G TUNED
'09 GXP MSM M6 #1123 - #30 of 38 OPTIONED KOOKS, VCM, VMAX, PAT G TUNED.....SOLD
'08 G8 GT IOM S/P-VCM-OBX-UDP-TUNE...362/375....SOLD
'00 Formula WS6 Hardtop M6 1 0f 233...GONE
'12 FRONTIER KC PRO-4X, M6, LOCKING DIFF, BILSTEINS..SOLD
'06 SAAB 9-7x 5.3...SOLD