ECU Trouble

The 1UZFE EGR Delete Kit is available for sale here.
I bought a 92 SC400 with 146k miles about 2 months ago. I’ve been trying to figure out why it runs like crap. I’ve replaced spark plugs and ignition coils so far. Cleaned MAF and Throttle Body and still runs terrible, it’s hard to explain but it feels like it backfires after getting into the throttle a bit or it’s misfiring. If I mat it, it goes nowhere and struggles just getting to 60 for cruise, overdrive being off helps some but not much. Anyways i’ve seen the ECU’s in this car and some others are pretty known for being bad. So I went out and decided to check mine. Come to find out it’s not the stock ECU and it’s out of another car. I can see some kind of discoloration on the top before opening it up fully. So I took some pictures of the ECU and put it back, go to start nothing, I am aware that it won’t start the first couple tries but it’s not wanting to turn over at all now, it cranks just won’t keep an idle. Either way I believe it needs a new ECU so I wanna make sure the discolored stuff in the ECU is indeed bad before I spend the $800 on a new one, and even then i’m not sure if that will fix what’s wrong with it. Does it need it or am I wrong? I’m going to try and attach the images I took. If anybody can help me out would be GREATLY appreciated.

Won’t let me add photos, if anybody is familiar with ECU’s I would like to email you my photos. Thanks.