Changing full xforce require tune?

[Waz888v8]

I have a full Difillipo 3inch system in my shed, purchased it 2nd hand, my current system on vcm16 cammed ve is xforce 2.5 catback with 1 7/8 xforce headers, the car actually feels good with plenty responsiveness , however sound wise its terrible , if i bolt on the full difiilipo 1 3/4 headers, will the car require retune? I live rural so no tuners where i.live,

Got the same system with 3 inch hi flo cats full thee inch with 2 1/2 inch extractors really loud too loud but once the carbon builds up sound is way better but took around three months to break in no tune way more power I have a vy ls1 otr still have my maf sensor

 

[VESSVBLACK]

I dug up some paperwork on the dyno results from previous owner, when i bought car he said it was xforce 1 7/8 headers and 2.5 catback from which was on car when he originally purchased it, at which i measured the xforce headers off my car last night and was quite surprised that they are infact 1 5/8 2.5 outlets with 2.5" cats, with dyno sheet 457 rwhp

More interesting is my mates ve ss, same workshop , same cam setup, but running a full big boy difillipo made 2hp less than mine...

My point is the shop didnt even know correct exhaust size as they put 1 7/8 on dyno sheet when infact 1 5/8,

,if im thinking logically, the performance shop is fudging figures to keep customer happy or smaller 1 5/8 header and 2.5 inch catback as capable as bigger exhaust pipes

 

[vr304]

I dug up some paperwork on the dyno results from previous owner, when i bought car he said it was xforce 1 7/8 headers and 2.5 catback from which was on car when he originally purchased it, at which i measured the xforce headers off my car last night and was quite surprised that they are infact 1 5/8 2.5 outlets with 2.5" cats, with dyno sheet 457 rwhp

More interesting is my mates ve ss, same workshop , same cam setup, but running a full big boy difillipo made 2hp less than mine...

My point is the shop didnt even know correct exhaust size as they put 1 7/8 on dyno sheet when infact 1 5/8,

,if im thinking logically, the performance shop is fudging figures to keep customer happy or smaller 1 5/8 header and 2.5 inch catback as capable as bigger exhaust pipes

The full big boy system is probably overkill for that setup yea but 2hp tho, you’d never feel that minute difference on the road or racetrack even for that matter, it would sound tough tho I bet

 

[VS 5.0]

2hp ?

We're the climatic conditions exactly the same for each run ?

 

[07GTS]

even a couple runs with same vehicle will be in the 2hp+ range so id say they are the same

 

[gtrboyy]

Didn't think there were 1 5/8 pipes for ve-vf only 1 3/4 or 1 7/8 unless brand/make of headers are shite design that primary crushed down to fit