Not only will the TTI make great power on a average 400-500hp motor they also last along time and don't rub on the ground and they also have nice thick flanges that seal realy well really long. I have a set on my car after several of the cheapy sets.

BTW I don't buy that the 340 manifolds would even make much power on a bad street motor over the smaller manifolds, after extrude honeing them a bunch they only pick up a couple hp so I don't think ex flow matters much, the main power gains in the ex are going to come from the tuneing effects of the headers.