I currently drive a 2004 Infiniti G35 Coupe automatic with 236k miles on it. The car runs great so far. Previous owner kept it clean and maintained it really well. But I wanna start to add performance parts to it and I’m not sure it’s a good idea with a car with that many miles on it. So I was wondering if I should just buy a newer engine with less miles on it first? Would really appreciate the suggestions/help.

Unless you're going to add forced induction just run a motor until it smokes or blows up.

Start with the best cost effective gain, plenum spacer, high flow cat, tune.

So if I do decide to add a turbo kit or supercharger just get a new engine?

Not necessarily, you can usually get away with hone+rings+bearings and run an engine hard for 60k miles.

Of course something else might **** the bed but that's always the gamble.

I’ll take the gamble, thanks man!

Andy be aware that the cost of going FI in these cars is lots of money. Unless you can DIY a lot of the work a proper turbo build will set you back over $10K and a supercharger will still be in the $4000-5000 dollar range or more. Are you sure you want to drop that kinda cash into a vehicle that has over $200K miles?