The heat never gets hot enough in my 71 bay and I think I might have figured it why. I installed a "crappy" empi quiet pack muffler 2 years ago along with new heat exchangers. The heat wasn't that warm but I went about my way. Now I'm looking to replace that crappy "very rusty" empi pack with something nicer and I realized today that the fresh air hoses from the fan housing connect directly to the heat exchangers via an aluminum hose and "Bypasses" the thingamajigs that lets the air wrap around the #2 and #4 heat exhaust for warmth on the original muffler. I don't know what they are called, its those puffy looking things that you can pry out the tabs to take off the muffler. Does this make sense about my heat dilemma ? Trey