The 2.5" section of your exhaust was your only limiting factor. I'm sure a little more top end power could've been realized, but it would've been so minimal you'd probably not even notice any gains. I still feel that removing the cats will be the biggest gain to be had. We don't own race cars. We own stock-block 2.0's huffing a little extra boost. the rest of our exhaust is just fine for anything our STOCK block will be able to handle. However, that's just my opinion and apparently my PROFESSIONAL experience doesn't mean anything. On a side note my 1976 Pinto with 2.5L EFI turbo was running 277lb/ft @ wheels. I stepped up to a full 3" piping and lost almost 30lb/ft. Horsepower increased a good bit around 5000rpms, but the torque lost was very noticeable. But what do I know?