Hi all, Have a tuned BA XR6T with Nizpro 4" exhaust and upgraded intercooler. It runs beautifully around town but on the freeway between 80-100 it starts to shake violently and the exhaust gets louder, almost starts to boom. The problem is, it doesn't happen all the time. First thought it needed a front balance but that didn't fix anything. Really cant work it out, especially the exhaust getting louder (cant hear each other talk) This goes on for a few K's then completely disappears. Sometimes it comes back, sometimes not. Driving me mad. Hope someone can shed some light. Ta, Steve.