TBI Surge/hiccup at light throttle

[legionwagon]

I've got an odd one, so sit down. Got frustrated with a really nice 1990 olds wagon (don't laugh!) and changed it from ecm-carb to a TBI system based on 1988 chevy 350 (a donor truck). It's a fresh olds 350 with a very mild cam. Olds electronic dist, cat and air pump all intact. Did great on emissions test, but was hard to keep at RPM. Starts great, runs fine until it warms up (presumably when it goes closed-loop, since if you fool the temp sensor, it runs better). Then it wants to have a sort of a large flat spot at light throttle (on highway, slight incline), almost undriveable. Occasionally will bog badly at start-off acceleration, hard to restart (bad thing to have happen at intersections).

 

Could a very mild cam upset the TBI computer that much? I have lots of extra parts, so I tried swapping out the following: ECM, spark advance module, oxy sensor, temp sensor, map sensor, ignition module(in dist).

It uses the Olds coil-on-top distributor (worked fine before), has a (painless products)speed sensor, electric inline pump.

Unless it is a problem with the cam (which I doubt), I feel that it is something small and stupid.

Any suggestions?

Thanks!