Be very careful with what you mix when it comes to long tubes. Some combo's don't sound well together. A guy on myG37 had an Amuse Exhaust and mated to FI LTH and the combo didn't sound nice anymore he had to sell the LTH's. On a friend's FI CB though, it sounded eargasmic.
+1 on calling Tony@FI, but tell him Sam from Dubai sent you