Oh right, I get you now! It's exactly the same age as my old one but 30K less miles and it drives like a much newer car although I think the suspension feels softer... but this could be due to the tyres?! Both manuals.
I'm more inclined to go with a potential boost leak. With the old one you could floor it and it would have very slight lag for a split second and then go, with my current one you floor it and wait about a second then it picks up, obviously 1 second feels like an eternity when you are use to something much more responsive.
I unfortunately don't own the old one anymore but I can take some logs of my new one and post back.