Not by me, not sure what the previous owner had done, its stock bore and pistons which weren't too bad but 177k miles I bet somebody got in it before and just did a stock overhaul. It almost looks like there was a saddle bearing used buts hard to tell because of how hard that crank tore up that...
So I had some issues with smoking after idling for a bit so I did a comp test and had 90 across the board dry and wet so I decided to yank the head. I found some leaky valves and the composite headgasket was a mess, which was what I thought. I figured while I was here I would fresh up the bottom...
As long as it is a ECU out of a 95 96 or a 97 you would be fine. The 98 and 99 (blackbox) ECU's are different. I believe the CAS/firing order is different and would require you to swap plug wires around.
I had the same exact issue that you are having when I bought my current DSM (99gsx). I went through and checked continuity, replaced/swapped coil packs, replaced plugs, plug wires, cas. It ended up being the ECM. Do you have another one available to swap and try?