'90 Suburban, LO5 350.
A couple of months ago, my engine blew a head gasket, and while I had the heads off, I installed some ported small-chamber TPI heads, and an upgraded cam (204/ 214, .420"/ .443", 112 split).
Of course, the factory computer is confused by the strange MAP readings from the lower vacuum signal (15-16" hg @ 750 rpm), so I needed a chip.
I've tried FOUR of them, and none of them worked. Every time, the engine goes into "limp-in" mode and runs worse than it did before.
SES light stays on or blinks like a strobe-light; cannot retrieve any codes.
Reinstalling the factory chip eliminates this.
I've gone through the whole diagnostic procedure for this condition (from an official GM service manual), and every time it comes up being the fault of the PROM chip.
The tuner has tested the chips, and swears that they're good.
For whatever reason, this truck's ECM just doesn't like tuned chips.
At this point, I'm about ready to slap a Quadrajet and big-cap HEI on it and call it good, but that seems like a huge step backwards to me.
And I'm not getting rid of the cam.
Anyone have any arguments to keep the TBI?