Interesting that you lot overseas find no gains with a sports cat on the ST170... I believe you already have a high-flowing catalytic converter on your cars, whereas in the States, the cat pipe is more restrictive. We always see gains with a sports cat or de-cat.

Vernier pulley on the exhaust cam will allow you to adjust your cam overlap. I've never seen it a necessity on standard engines, but with a turbo or supercharger, it helps quite a bit to be able to "dial out" excessive overlap.