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have no idea, worked NA ecotec do as they have potential for more than 350Hp at the flywheel with relatively mild work.

pre ecotec are a fair bit less with their more restrictive heads.

And for stock, I have no idea but I imagine no difference from single to twin as the stock pre ecotec doesn't make a whole lot of power.

I heard going too big on these actually looses power from lack of gas velocity. I am actually very interested to see if any decent gains are to be had when I get the spark done on the dyno. VE table should give me an idea how much more it flows over stock exhaust when I get to that point.

I always felt good torque gains at the bottom end with just pacemakers and no tuning, so I am hopeful.

v6s love a full twin 2.25" exhaust

delcowizzid wrote:v6s love a full twin 2.25" exhaust

but with other mods or just stock engine?

doesn't matter, keeping the pipe size the same as your header outlets all the way through is important, going to larger pipe, eg catback causes the gas's to cool and slow down as they enter the larger pipe. Also joining the banks into single pipe would have a performance hit unless you can design it right so they dont collide with each other, again slowing it down and usually causing more noise. Also putting a small H pipe in just after the end of the headers can help extraction further, the rush of gas past the H pipe will create a vacuum on the other bank.

I noticed all the off the shelf systems are 2.5, I think the pacemakers are 2.25 ?

So with 3 to 2 to 1 system, the 2 to 1 is ok if its a merge?

round cat or oval cat? which work better?

if it's boosted then you'd get 2.5" twin, headers with 2.5" outlets. 2.25" for N/A.

If your going catback then go and find a VX/VY cat, they are proper twin inlet atleast then run the 2.5" out, will work much better than trying to use single ones on earlier models.

So would i be better off, having my Y pipe modded for twin cat and have straight though pipe where the old cat was?

I don't think 2.25 sports system even exists for VN-VR, all I could find are 2.5

VX/VY Cat like in this ebay, just have to join your existing Y pipe in, then dump your 2.5" on the outlet.

http://www.ebay.com.au/itm/Vt-vx-vy-3-8 ... ca4&_uhb=1

Ok, so looking at the system, it goes 38mm primary, 50 secondary, 57mm tertiary to the cat.

There is no room for twin cats on the y pipe, twin inlet cat could work but will require re doing the y pipe as the shape doesn't suit the VX cat.

To be honest I can't be bothered with it lol, might just get a good flowing cat.

The dilemma I am having is, where do I find a 2.25" mandrel bent sports exhaust, searched the net high and low, only 2.5" grrr!

if you can't do two seperate cats (one either side of the gearbox, then in my opinion its not worth it!