if its one of the fitter type places walk away (particularly Formula 1) as the quality of the parts is very poor
I agree with that!!! if it's Humphreys then run as fast as you can. They charged me £730 for a complete 3.0 system. Didn't kmow about Timax then but I do now. They had to fit a different make two weeks later. They don't believe in gaskets there. I'm getting a new Vx one fitted by someone else next week. Three systems in 2 months!
The Walkers system fitted to my V reg lasted less than 2 years and cost more than a genuine one (on trade club).....this was Formula 1 auto centres.
The quality of the fit was appaling and the part that failed was the baffles......on all three sections!
The V6 system does not use gaskets (excpet on the front pipe/cat to manifold join).
It is important to make sure the front pipe to centre section flange is nice and clean and I use a smear of good quality jointing compond to. You also want new stainless steel bolts for the centre section to cat joints (4 off) which are M8 by about 40mm from memory.
Then you need a smear of jointing compund for the centre section to back box joints to.
The hardest thing about doing a V6 exhaust is undoing the centre section to cat bolts, sometimes they snap off (if crap bolts have been used last time) and the worst case scenario s that they need drilling out howver, I have always managed to remove the buggers with some heat, some rust flash spray, a good clean with a wire brush and molegrips if this happens so its worth advising any fitter to heat the bolts up before trying to remove them.
Other than that its an easy job, hang the centre section on the rubbers and bolt them loosely to the cats, fit the tail section but, dont tighten the clamp. Check its all central and not rubbing against anything (you can get quite a bit of adjustment by altering the centre to rear section joint) and then tighten it all up a bit, give it all a good shake to make sure its not fouling on anything before tightening everything fully.
Also, get some 2-3inch stainless jubilee clips and put them round the bottom of the heat shields on the cat sections to stop them rattling.
Job done.