As I had asked for some help a few months ago, thought I'd post the findings. Thanks to everyone that replied.
Here's the scoup-
'89TII I purchased new encountered periodic detonation under a load. Idle was perfect and car would accelerate without a problem to 80/90 MPH as long as it wasn't WOT. Everything I checked appeared normal. Fuel pressure, all electrical, exhaust etc. Took it to KD and initially, everything checked out ok. Compression was a little low, but equal throughout. Finally when taking another compression test, probably the 3rd or 4th time, a sticking apex seal reared it's ugly head. This was a tough one to find, because it didn't stick all the time.
As the car has 156,000 miles, excellent condition, I've elected to install a new engine rather than try to loosen up the seal, which would probably give me some more time.
Got to thank Dave for all the help. Great guy to deal with.

 

congrats sort of

 

So under full WOT the seal would leak out compression causing the car to run lean?

New motor ? - why not just do a rebuild on the current one.

 

The spark would go past the seal into the next chamber causing detonation.

If the engine is apart & rotor housings are needed, they're about (don't quote me) $400 each. '89 TII engine from Mazda $1800 plus shipping to KD $60 + return shipping for core $60. At lot less aggrevation plus starting with "new" components.
If I were doing it myself, I'd pull the motor apart and check what was needed and probably rebuild it. Being older and not wanting to get involved with pulling the engine etc. thought this best way to go.
I had my share of rebuilding/racing piston engines years ago. Thought I'd never have anyone do an overhaul on my motors, but as you grow older, you become a little more lazy.

 

hmm.. that's interesting.. maybe the ATF trick could be on a "regular" maintenance schedule

 

Actually a combination of ATF for lubrication and kerosene to desolve deposits was the order. Let sit a day and then turn 1/3 each day.

 

you should pull the old motor apart, i bet you would find an apex seal the was cracked in the middle, ususally they will break a corner off, or shatter. sometimes you will see one that just splits in the middle. the car will run ok, not great just ok, and it might have the symptoms you describe.

mike

 

Mike:

I also would like to see what the problem was. If the car was at my garage, and as I said earlier, a little more energenic, I would like to investigate.

Don