When I had my 97 GTS with smooth tubes the car Dynoe'd 473 rwhp and 542rwtq. This was done on the same type of Dyno. (aka Dyno Dynamics).
This can give you a reference. Not to Piss in your cornflakes or anything, but it is a 10% correction compared to a Dynojet. My car is/was suspected of having an arrow rebuild as it put down abnormaly big numbers for being essentially stock.
Still it's great to see a Gen II putting down some solid numbers. Try a Roe Racing Prom and maybe some headers, get the numbers even higher.
Congrats on a great car.