I have a 93 CRX/del sol (B16A) DOHC VTEC and notice that when VTEC engages it doesn't scream as hard as the CIVIC VTIR (B16A engine as well)..

My brothers mate is a mechanic and took my car for a spin, he said vtec is not poping as hard as it should, and that I needed to change something to do so... My current mods are - extractors, exhaust 2" piping, HKS air filter and Ceramic coated air intake pipe, Power chip gold. I don't know what to change, any suggestions or has anyone had the same problem?

Also I wanted to get 2.25 inch cat back piping but they said that I would lose power, but I've seen & read about alot of crx, civics and integras with 2.25 & 2.5" piping.. What would you guys recommend?