if you run a t25 at under 8psi on a good ka, it shold be good and not to unreliable. but anymore than that and you are taking some risk's. like i said before, the 2 things i would replace that are the weakest links in a kat are
1st the head gasket (even if you only want 200hp). and then the pistons at anything really above 300hp. in all reality if you have good pistons and a good hg then the kat should be nice and reliable motor till about 350hp. it seams the weaknesses on the ka don't really start to show themselves until about the 400hp mark. after that it gets alot more involved. needing bigger head studs, rods, head work, oiling work ect.