Hi all first time user so be gentle with me!.

I've just put some aftermarket stainless downpipes on my Thundercat they went on well but when I started it it was blowing badly from the manifold seemingly from every port. I've tightened the nuts as much as I dare but it's still blowing. I didn't use new gaskets as the guy said there was no need and the flanges on the new exhaust are much thinner than the original.

I'm at a loss to know why it's blowing so bad any ideas would be greatly appreciated.

Cheers

Try fitting new gaskets, the bloke that told you otherwise needs his head read. If the flanges are too thin you may even need spacers.

Make sure to have a real good look at the old and the new to compare and make sure that that the depth of the flanges are the same. Always use new gaskets when going to the trouble of replacing parts etc, same for O rings. Dont chuck away the old flanges, it may be that youll have to fit them onto the new pipes to get the correct seal. I had to do that once when I fitted a ss system, the new flanges were crap