Any ideas for a full 3" decat exhaust with headers and uppipe that will pass trackday noise restrictions ?

 

Harvey Smith can port your std headers for you and supply a very good up pipe that works very well, an alternative is the GT spec headers from the likes of ScoobyMania, but these tend to work better with bigger power cars. Ported headers would be better up to about 350bhp
The rest of the exhaust, i personally run a full 3" decat, the down pipe is by RCMS and it's mated to a Revolution system, i find the combination works very well indeed and is not too loud so should pass trackday regs with ease