Re: Compression test on '89 - 2.9L
Depends on how it's checked. I usually check when the engine is cold and don't mess with the throttle (either because I don't care or the engine isn't in a state to be ran). You can get higher numbers if the engine is warm and throttle is open. But variance is what you're looking for. I wouldn't worry if it was 110PSI as long as the numbers were consistent. If it runs, it runs.
Might be right about carbon build up, I rebuilt a 2.9L and was 175PSI across the board with fresh cylinder walls and brand new heads. My 1993 Tempo gets 130-135PSI with 180K miles on the clock. I would expect more or less similar results on an aged 2.9L, but then again it depends on how the test was done. Could try and Seafoam, but really wouldn't worry much about it unless you think it's contributing to a problem.
1987 Ford Ranger Short Bed 5.0L/T-5 Project
1988 Ford Ranger Long Bed Parts Truck
1993 Ford Tempo 2.3L OHV HSC Auto - D/D Stock.
1999 Honda Accord VTEC Auto
2002 Dodge Caravan - 3.3L Auto