I understand preventative maintenance, but based on this, and a "recent" headgasket job by toyota:
Perform a compression/leakdown test
Fix all leaks (fluids, boost/vacuum)
Ensure you have proper oil pressure
Replace fluids, worn belts/hoses, etc.
Enjoy, and then look into basic mods as your knowledge progresses.
Easiest and most noticeable mod is a free-flowing exhaust.
The right way to do it is of course pulling the engine and completely rebuilding/refreshing it, but it seems like you're not at that point. If you don't have the knowledge, you could end up spending all the money to rebuild it and end up worse off than you started. The same goes with using a mechanic unfamiliar with the 7M. If the engine checks good, there's no point rebuilding for ~300 hp goals. Enjoy the car, don't beat on it like it's unbreakable, and like many have said before, keep a close eye on oil pressure and coolant temp.
You guys school me... I'm looking at down pipes. Do down pipes typically have the turbo elbow?
Some do, some don't?
All the same?
I was advised the one I was looking at didn't replace the "most restrictive part" which was the turbo elbow. Is this correct?