parts that will give me the biggest hp increases

[wikdMK3]

i just bought a 89 n/a supra. its got custom 2.5 catback exhaust with an aerospeed muffler, k&n intake, modified afm, and an eibach prokit.im looking for the parts that will give me the biggest hp increase, i was thinking to finish the exhaust and get a header and hi-flow cat, but if anyone has any suggestions they are more than welcome.