Could be the ECU, could be the TPS, and really it could be a lotta things. But with no codes to guide us, it can be an expensive game of hit or miss.
If it was me, at this point I would double check all vacuum lines (I remember especially those ones up under the intake manifold, and the junction at the front of the engine) and then just drive it for awhile, trying to force a code.
If nothing comes back, and pride prevents a trip to the dealer for a diagnosis, I would probably swap the TPS first, based on cost.

__________________
Prost!