MPS3 series 1 and Hurricane dump pipe...

Apologies if the FAQ's answer this, but I've read as much as I can find.
SO...I have a K & N SRI, a Hypertech tune removing 1,2,3rd gear torque limiting and enriching fuel mixture slightly, apparently to keep EGT's down. (didn't fiddle with idle, redline, or top speed).
Now I'm adding a 3" Hurricane split dump pipe and hi-flow catatytic, and bolting onto the stock 2.5" exhaust. Am I correct in the impression that most HP & torque gains are made with the 3" split dump pipe and hi-flow cat, and the stock exhaust is less important? I can go with a 3" exhaust if it's really necessary. The system will be in mild steel. I felt the stainless CPe Turbo-back was overcapitalising, seeing as she's already done 250 000 km on freeways, mostly.
Cheers in advance, Chris.

You're going to hate the answer to this, but a hypertech doesn't gain much from a dump pipe... As it's a load based tune (IE airflow at rpm) designed for a stock exhaust system, if you are hitting your targets you won't gain anything extra from adding more mods...

Yeah that's good. Thanks for your input. I realise I'm digging a hole I may not get out of without a load of cash. I'm not going the dump pipe and hi-flow cat, as we expect a warning light and limp mode etc. Might stick with stock and go for 2nd cat delete and hotdog muffler. Comprende!

If I could have my time again, I'd most likely just go with a 2nd cat delete (race/test pipe) and a larger than stock intake from day 1...

Followed by Hpfp + AP + e85 or meth tune... (Currently DP + intake + e85 tune atm)

Sometimes miss the pull to 6500 from my old BT, but this is much nicer for day to day driving

+1. I'm still running stock downpipe + calls recepipe, 3" intake and tune. 20 psi, 300 airflow and plenty of power for daily driving and still have e85 to try. Id only go through the hell of a DP install if I was doing turbo at the same time.

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