Welcome to the board!
The first mod you will be needing is most definately a logger, as it will allow you to read the datastream and locate any issues with what the ecu is "seeing".
To troubleshoot your problem, it would be best if you start with some basics.
A big help would be if you could post a pic of the ecu board, as it may still be on the original caps, or there may be damage from the previous caps leaking.
The t/e/l ecu will "work" in our cars.
The fuel trims will be a little off because the ecu isn't expecting the lower honeycomb to be missing, and the curb idle on the t/e/l units is a little lower.
These are small differences, and will not cause a problem such as you are describing.
That said, just because it says it's one number on the case, doesn't necissarily mean that's the number on the board, or that it's the correct unit. Posting up a pic of the board with the number on the harness connector body visible is worth a thousand posts on the subject. If it's really a 6262 series unit, the number on the connector should be 6578, (with a bonus if there's an "e" there for e-prom)
For the problem you are describing, I would check the ecu temp sender wiring at the thermostat housing. The wires there get brittle and break and then the ecu temp compenstation will be off, and it can lead to trouble like you are describing.
After that, check your coils, ignition transistor, and cas for issues with the harness/connectors and the like. Repair any bad wiring before replacing any components.
Definately check the whole car over and verify that the basic maintainance has been done. The t-belt is mission critical, and you should verify it has been done recently. If it hasn't it should be job #1, along with the caps in the ecu.
Good luck with the car, and welcome to the board. /ubbthreads/images/graemlins/smile.gif