Pacemaker long primary extractors, down into 2 1/4 twin hi-flow catback system, 2 1/4" out of each hi-flow cat merge into a single magnaflow center muffler, then straight pipe after that, best VN V6 exhaust you'll ever hear and powerwise...
Next thing, Throttle body which you already did..
Someone suggested powerchip off ebay, Don't trust them off ebay there cheap rip off's with incorrect flow for spark advance. Get in contact with Greenfoam on this forum and tell him HoZy said you can do a "Titanium" Performance chip. You'll love it.
Stage 2 shift kit.. It's a definate, Get the band's in the gearbox re-alligned...
If it's a six get some 1:7:1 yella terra roller rockers, it'll change the compression ratio a bit and it'll love the exhaust system and chip
All these ideas are recommended 95RON fuel minium, as soon as you hit the chip...
Cheers
MaT