oi8228oi said:
go with the strait pipe so you get that great rumble and the whistle, or maybe some stacks
umm, if he already has an 18" glasspack muffler, then he already has a straight pipe.
many of us run Walker Big Truck Mufflers, BTM's. glasspacks w/o the glass. the benefits of a 4" system for 1/4 the price.
to answer your other questions- you don't need gauges unless you mod the truck up and work it hard: put a chip on it and tow a 5'er or the like.
you want to keep an eye on things like EGT;s, trans temp, boost, etc,,. conventional wisdom says these trannys don;t like heat at all, so a real temp gauge on the trans is a good idea in addition to the pyro.
dennis