Do you think the fuel injection is responding differently than a carb? It seems like conventional wisdom is that the TBI unit should behave like a carb.
From reading the Pontiac engine building books and all the posts I could find from guys like Cliff that have extensively tested and documented changes, I expected the open spacers to cause idle quality to suffer and off idle response to be sluggish. I expected vacuum to be lower and MAP readings to be higher. I did expect a better seat of the pants at upper rpms.
I did not expect the results that I posted as they were opposite of what I expected. One other thing that seems to have changed with the open spacer is that the AFR adjustments are smoother. I have a dash gauge for AFR as well as the injection hand held. With the divided spacer, the analog gauage was real jumpy. It would jump high and low around the desired readings but was never smooth. Now it is much smoother and linear in its readings. With the divided spacer, the system seemed slower to respond. For example, if I'd change AFR set points it would take a trip or two to town and back to where trims would stabilize around +/- 3%. With the open spacers, adjustments seem to come faster. After each spacer change, the trims would be back in range within a half trip to town.
My goal in testing has been to play with different combos and see how much clearance I might have to make a performer RPM fit as I figured the larger runners and taller plenum might work for my combo. I figured on a street driven engine keeping the plenums separate would be better hence wanting an RPM intake.
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