just wanted t know and i assume it will does 6g74 bolt into the tr ok? will it bolt to the gearbox properly?
as i said seeing as though it used the 6g72 same as the 3ltr 3rd gens it will be fine

how would the ecu handle this?

It doesnt work easily unfortunately

For starters the third gen s4 motor is totally different and will not bolt to a second gen box

There are many differences to the point where a third gen motor will not bolt in

The 6G72 in the third gens weren't the same to the 6G72 in the 2nd gens, the only 6G74 that will bolt into a 2nd gen is the really early model mitsubisbi pajero motor, finding one of those engines with low enough ks in a condition worthwhile is hard.

If you want more power, you could go for a non turbo 6g72 out of a Mitsubishi gto or a twin turbo 6g72 out of a Mitsubishi 3000gt

The non turbo has a 154kw engine and the twin turbo has a 207 kw engine and both bolt straight in but expect to still spend quite a bit of money making everything work (need ecu, strengthen auto or go manual etc)

The motor you have now isn't actually that bad for power assuming you have the 6g72 v6 2nd gen tr, you can get more power out of it just by putting in a freer flowing exhaust, maybe an ecu chip... Uhh and that'll bring you up to about maybe 140-150 depending on the tuner that does it... And would still be cheaper then buying an engine and getting it fitted.