Intake, exhaust and boost controller are a good place to start.
For the exhaust, an easy way to go is to just buy a Trust downpipe, or a 1JZ downpipe for a Supra that is premade, period - it will bring the 1JZ downpipe to where a normal 7M downpipe ended under your car. 1JZ and 7M Supras use the same cat-back exhaust systems; the downpipes are just different to facilitate this.
After you get a downpipe, a bolt-in "test pipe" would be ideal, and then either a custom exhaust from there, or you can get a bolt-on one from a company.
A full 3" mandrel-bent exhaust on it's own should net you some decent gains.