a leak down test is your best friend for telling what kinda health the engine is in. (Compression tests don't show everything)
If you are worried about the ECU stuff, contact who ever you are going to use for tuning in the future and ask them about it.. Otherwsie, With a small paid subscription ForScan can flash your ECU back to stock.
That just might have to be the route I go for the tuning part. I'm thinking that may be a while in the making, though, given where I'm at with the engine.
New problem arose today. Hood release cable pulled through into the cabin at the end of the day a couple days ago, and now I can't get the hood up. I had the hood taken off, but laid it back on it to cover it up for the night. Now it's latched all the way down, with no access to get to the safety lever part. I can reach the actual hand-actuated lever, but not the one the cable moves. So before I break either the hood, latch, or bumper to resolve this issue I was hoping somebody else had run into this and knows a trick.
The other half of that would be; when I can't get it open the right way, which part do y'all think breaks first when I just start wrenching on the back of the hood to get it free? Also, anybody ever seen a MS3 with a hood that opens like a Viper? This might be a first. Pity I can only do it once, I suppose.
And where do y'all think is the best source for replacement parts like the hood latch, cable, etc. after this is worked out? I see a few sites online advertising real or OEM Mazda parts, but I'm suspicious of everywhere these days.
Thank you all for the advice and insight, I absolutely wouldn't make it through this project without it.
***Edit to add since it won't let me post again***
Joking aside on the hood issue, I was able to fix it with the help of my father-in-law just now. Apparently it's a 3 handed operation, but I was able to remove the latch assembly from under the car and pull it off with the hood.
I am still curious where y'all recommend getting quality replacement parts, though. I'm finding that whomever had this car last did a number on the engine bay and I have all kinds of missing or broken bits and bobs that will likely need to be replaced as the project goes on. I'd like to have this as clean and complete feeling as I can, with just enough power and noise to make for a rowdy daily when I want something a little less refined than my normal ride. So making sure it has all of its pieces and having them intact is an important goal for this build, I feel.