I own a 1989 Chevy Suburban, 4X4, 1/2, with a new 350ci crate engine and a new transmission (700R4). In the 3 years that I've owned the vehicle, it has had a problem with episodically flashing the "SES" light which seems to be activated by some vacuum related issue. It lights up most often when decelerating from freeway speeds. Various codes have been detected including MAP sensor, TPS maladjustment, and others. However, all of the components in question check out correctly, contrary to the codes. I'm baffled. The vehicle performance, while passing emmissions with no difficulty, is well below what I'd expect. It actually runs as though the ignition timing were severely retarded though it is "on the mark". I've also recently replaced the T.B.I. with a new Holley unit and it, too, is adjusted properly. Note that this problem has been present with both the original engine and the new crate engine. One person I spoke with suspected a ground problem. Any suggestions? Any and all input would be welcome.