Thank you all for responding. Looks like Patrick might win the 'long distance diagnosis contest' this time!
Steve, (a mechanic - not the owner) from Steven's Auto Electric & Machine Ltd. went for a test drive with me.
He tested the TPS & showed me the voltage was erratic, which could cause the symptoms.
The root cause of the erratic readings isn't necessarily the TPS itself; the throttle shaft has too much play in it.
Voltage readings would vary from wiggling the shaft without rotating it. Hence no ECM codes.
We'll see if a new TPS will resolve the issue or mask the symptoms. If not, the TBI shaft play issue may have to be addressed.