Well... i'm going to "probably" get a custom straight pipe from the bottom of my shorty header to my catback exhaust... now my exhaust is a Greddy Evo with the 60mm piping.... now if i get the downpipe upgraded to the 60mm piping from a friend who owns exhaust shop and no cat.. just running straight from header to exhaust piping??? how much gain will i possibly get... like will it be a decent ass dyno? better high End?? better low-end??? how much power increase on the 1.7L? Thanks

-Derek