I recently underwent a project a long time overdue on my rig, the installation of the GearVenders under/overdrive & a new design exhaust system. First off the people at GV are VERY confident & knowledgeable about their product & for good reason. I am delighted with this product & I'll be putting another GV in my Classic Chevy soon. The noise reduction & fuel economy benefits are long term investments. With fuel costs & niose stress reduced this is initally expensive but worthwhile in the longrun. My compliments to GV. I do not have any MPG figures yet but already my gas stops have become fewer than my previous routine. Now about the exhaust. I used the Hedman "ELITE" hedders going into flex unions, back to the "X" cross pipes & through one set of DNA stainless mufflers (with 95% flow rate) & finally a set of Flowmasters. This setup is very quiet & durable. One could use any other type of mufflers to achieve comparable results but the "X" design balances out the exhaust pulse & raises the note to a less audible level. Your engine WILL sound & run very different & smooth with performance you can feel. This design is comparable to the ones you'll seeon NASCARS & many road & Track vehicles. It's nice to be able to enjoy the technology available today & not have to settle for less than standard equipment! All for now, I be back with more soon. Happy Motoring Steve