My 91 with 50,000 miles is an occasional driver. Kept indoors and warm when not being driven. To be prudent I finally had the timing belt and associated items replaced by a skilled responsible independent mechanic.
He found everything including the old belt to be in excellent shape. Nothing showed and signs of significant deterioration.
All parts installed were oem and were direct replacements except there was one belt cover section that was replaced by an updated version. He was not able to replace the cam seals which showed no signs of leakage.
The motor now emanates a whirring whistling sound ? It "seems" to come on more so when the engine warns up and follow rpm's.
And to be coming from the belt cover side of the motor and not from any ancillary component. He says everything went back together just right with no strain or stretch required.
Also and probably independent of this situation is the fact that the motor does not run smoothly at idle. To be fair it has loped along not holding an even Idle occasionally even before recent work which included new plugs and one plug coil replacement and some AC Ventilation work.
The valves could stand to be adjusted but are close to tolerance.
Does anyone have any ideas where next to look on either of these?

Since this was posted a while ago, do you have the issue resolved by now?

the mechanic can't diagnose a noise? you sure you have a good mechanic?

Hopefully he has found a better mechanic by now.