OK, here's the scoop. Got an '86 IROC. '86 harness w/TPI. Aftermarket TFS 23* heads and Edlebrock TPI base, no cold start so I have '91 SLP runners and fuel rails, and I'll be buying an sftermarket throttle body, probably a 52mm BBK unit. So the base, runners, fuel rail, etc will be for a non-cold start car. Should I use the '91 SD plenum with the setup or my '86 MAF plenum? I'm just worried about which passages in which plenum are correct. The system will be programmed as an '89 MAF car, and if I do use the SD plenum, should I go ahead and use the earlier throttle body or the later? I just don't want to mix anything up...thanks for your help

 

From everything I have read, your plenum should work just fine. Good luck with it!

 

You'll have to use the '91 plenum since the '91 runners don't have the idle air passage in them (goes to the same place as the cold start injector). The '91 plenum and TB are different in that the idle air goes straight into the front of the plenum instead of through the passage on the underside of the plenum that only the older plenums have. Also, the '91 plenum has the extra hose nipple for the MAP sensor, which the '86 plenum doesn't have.

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Greg Westphal
'87 IROC 355TPI/A4

 

Use the 91 plenum and the 89-92 throttle body.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
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