Biggest exhaust manifold for N/A

[Wobba]

Where is it, how do I get it?

Making one through a specialist is going to be expensive I imagine?

[B00ST]

Well a tubular manifold for the F4R is going to cost you over £700, it is a work of art though. I'd speak to RSTuning, but personally I don't see the point, I can't see it gaining much power. Sorry to say, but if you want a decent jump in power you're going to have to look at going boosted. Which isn't a bad idea, as you can still have a lagless big BHP setup that drives pretty much NA, even with turbo's.

[Evogone]

Too much money get a Willy on for mid range and a supersprint for top end.....I got a Gp.A one from France but look identical to a supersprint. Get a 2.5" dia exhaust thought this makes a big diff on a high spec engine.

[Wobba]

Yea, it is why I am tempted to put the Oreca back on the car and silence it a bit for road use. It is slightly bigger bore than the Mongoose.

[Evogone]

I put a better silencer on mine and its quieter but still make the same power.

[cliokongen]

If you can get a hold of a Megane Cup manifold (which looks like it's got a bigger bore than any aftermarket manifold i've seen) - do a few mods to it and that should work nicely! (thats on my to do list - got the manifold, just need to do the mods and fit it)
Other than that - as Evo mentions 2,5" bore is the way to go on a high power NA build.
Makes such a big difference.