removing the cat is a big improvment in performance for the celica gts! but unfortunatly the ecu clamps down on the gains after a few days.the only way it can be done without the ecu messing things up is to get one of those devices that immitates the second o2 sensor(showing a normal reading of o2 to the computer).
i've heard of these, but where can you find one for the celi?
you can search the forums for the info on how to make one or you can contact splitsecond.com this is a partial clip message from splitsecond.
"We have the ESC2 which connects to the rear O2 sensor(s). It keeps the
>check engine light from coming on when you take off the cat.
hope you get it soughted out,its an awsome feeling with you cat out,right!