2 1/2 " downpipe? from the collector?
thats too small dude!
and the cat you replaced the stock cat with (might say hi flo. but hi flo as compared to what cat? those on civics,accords,tercels etc.point.the celica cat is a hi flow cat! a very good one too you see the size of that thing?.take a look at the celica cat the diameter and compare it to the dimameter of the hi flo one and take into account the material on the inside. if you can come up with the hi flo cat is still better,then maybe it is and let me know which one so i can get one
as for the resonator you might not be sure if its really flowing more.
when changin exhaust parts/components its not a good idea to guess and buy stuff,esp. with small displacement hi specific output engines like the 2zzge(those guys at toyota tried to squeeze as much hp out of the car within a certain noise level requirment)
did you feel any gains? dont just go by it feels better low down,does it feel better up top as well,is the car revving quicker?
btw. the resonator.is it perforated,or is it louverd(with swirls,and rises on the inside,what is the bore dimeter as compared to the stock one) all this and the welding can contribute to exhaust noises.
why dont you post a pic of the set up.