thinking of changing my back box on my sti,will it need any tinkering when it's on??what about back pressure

 

No if you stick with the standard size backbox all will be fine. The ecu will self learn within 100 miles or so.

Back pressure won't be lost unless like me you fitted a straight through pipe - basically scaffolding poles and then you run into difficulties!!!

 

nice one the back box will be 4.5 at the mow it's 3.5 and yes it is straight through and de catted

 

The only thing you need to check is that teh flange sizes are bothe the same on the centre and backbox..

Rob

 

cheers for that rob will do