Who knows what ecu system would best suit my Magna it 98 tj 3.0 v6?

Also has a 2 1/2 in sports exhaust

1. there is no such thing as a 98 tj? i think you have a tf or th.

2. what do you mean? whats wrong with your existing ecu? If you want your car tuned just tune the existing ecu. If it cant be tuned dont bother because youll only gain a few hp

If your car is a 1998 model TF, there is a chance the ECU is reflashable (TH/KH and later are all reflashable). You need to see whether your car has a white rectangular connector on the inside of the bottom edge of the dash half way between the steering column and the centre console. If it has such a connector, the ECU is reflashable.

In general you probably need other mods than just a cat back exhaust system to make it worth while investigating tuning options.

I have a haltech straight out of a 98 tf that will plug in and run the car