I just saw a TBI spacer that had the bores opened up into one, they said it helped increase power. My question is would it be possible to siamese the bores in the intake as well, or would I hit water?

 

Stock you could, but you shouldn't go down too far. Its not worth the effort to take off the stock manifold, do that, then put it back. Buying that spacer or making your own would be better. http://www.cfm-tech.com/OtherGMTBIPerformanceParts.htm

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-Tas
'89 Formula WS-6

305, TBI, 700R4, P.A.W. 14x3 open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips, Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248)
Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options