Tidgy

welcome 🙂

It's possible, but unlikley to be something else unless you had recently changed the rad or something similar causing the airlock. If its the same before and after coolant change then doesnt sound like its an issue with the cooling system itself . Check for any leaks on the rad, they sometimes get cacks and only leak when it gets hot, just to make sure. After that then your onto rebuilds. Clinic can give you an idea of that as you say, but i'd look at replacing the rods and pistons while its apart. Stock pistons are pretty crap and known to suffer ringland failure, stock rods will be fine if your staying near stock power, but anything aproaching 400 and your putting them at risk. Then other options like closed decking depending on how far you wanna go and what your budget is.

yes could well be that, although it's normaly affected by cold weather. Ecu has a default o feck, that aint right saftey cut, first it pulls back boost, second it pulls back fuel which feels like you hit a brick wall. Watch out for mappers removing these saftey features when you do have it mapped, proper dodgy thing to do but i know a few mappers who do it.

2.5 headgasket is a full rebuild job inc bottom end. 2.5k sounds very cheap, you sure clinic knew exactly what you were saying?

i cant see anything on teh rag other than oil?

10 is a pretty tight budget now adays for a decent jdm widetrack, prices have def gone up in recent months.

has it been mapped? sounds like it may be hitting boost cut, aka overboosting. cause could be any number of things.

welcome 🙂

P.s. I've just finished running in my closed decked, forged 2.5 engine clinic built for me haha

2.5 tuned right won't increase the risk if failure up to mid 300's. They have a high failure rate even left alone. Beyond that your pushing the limit, sti's don't have proper forged pistons any more, the rods won't take much more than 400 so 350 your Into forging territory.

i'd leave the front alone and upgrade the rear on it, not 100% sure on the standard size on a hatch, sure somene will be along to tell you. doing the rear helps with canceling some fo the understeer, so if you do both you balance it out rather than correcting it.

welcome. would of thought a decent local retrimmer could do it for you?

welcome 🙂

i know scoobyclinic fit perrin ones. they are a different fitment i believe

Welcome. Rust will be a big concern on cars that age. Rear arches are highly likely to be on the way out. Bear in mind they rot from the inside out so if any is visible then alot will be hidden behind it, don't be fooled by someine claiming it's only the odd bubble of surface rust.