I've just bought a second hand 3" bore HKS backbox. I want to leave my 2.5" downpipe on the car and was wondering does any company make a centre section that is 2.5" at the downpipe end opening to 3" at the backbox end? If not i will have to get the welding gear out.

 

HKS backbox is a different length but H&S are making me a centre section that will fit

 

i have a tsl sports cat dp (2.5) that fits to a HKS hiper (3) on my02 wrx and had no problem

 

I haven't got the HKS centre section though.