When running good, it should run 55-60 MPH easily.
The burning off of oil is probably valve stem seals. Most higher mileage 16Vs have that issue. That will not cause a poor running issue.
No sensors should have been changed out unless they were verified to be bad. I would assume they didn't test them and just started throwing parts at it, to see if it would help.
I doubt the PCM (ECM) is bad. The 96s weren't known for the common ECM issues like the early 90s ones were.
How many miles are on the tracker? With proper maintenance and common sense driving these motors should run 200,000 miles fairly easily.
There is nothing special about a trackick engine compared to any other engine out there, when it comes to diagnosing, tuneups, etc.
Sounds like to me the mechanics you took it to just wanted to swap a bunch of parts and charge you what I am sure was a shitload of money.
Of course I do not know any mechanics in your area, since I am not remotely close to your area. But I can give you some basics on what should be done (in my opinion), when diagnosing an engine that seems to be down on power.
Make sure the check engine light is working and isn't on. If it is on, work through the issues that the codes indicate until the issues causing the codes are resolved.
Compression check
Timing check/adjustment
Valve clearance check/adjustment
Test the various sensors
For tune ups, I suggest...
New plugs (I like the NGK brand)
New plug wires (16Vs are bad about spark plug wires causing poor running issues, in my experience)
New distributor cap and rotor
New timing belt (every 100K miles or so)