Welcome to the forum!
2500 isn't bad for a complete car with 94k miles. What about the body? If the body has more mileage or it's from the rust belt I would talk them down on the price. Tiburons in running condition are a dime a dozen these days. Whatever you do, make sure the timing belt is done every 60k miles or every 5 years. If the previous owner can't furnish receipts for a timing belt job, talk them down on the price some more then replace it immediately... or you will risk losing all your valves. Most of these cars are up for sale because a $500 pars+labor timing belt job is worth more than the car. Unbeknownst to the next owner they generally pop a belt and junk the car within a few weeks.
As far as tuning goes, there isn't much aftermarket support these days. The OEM ECM is tunable but that isn't public knowledge yet. Tuning the ECM isn't a problem for a 2004 with basic bolt-ons so you should be OK. Most owners bolt on a set of headers, catback exhaust and a cold air intake then call it a day. You can take it a step further and port your intake manifolds but you're only looking at 180-190WHP. Remember it's only about 170BHP or 140-150WHP from the factory. If you can manufacture your own parts or modify existing parts it's a great platform to learn from.
