21mpg in the city is crazy good. I haven't driven mine enough to tell what it's getting. I would guess 18 or so. It's stock but I am going to add a programmer or chip like you did. Not sure if I want to add exhaust. Don't want to blow much black smoke by not having a cat (I read your post saying your tune didn't have you blowing too much) and I'm not sure how much noisier I want it.

 

There is NOTHING in the line between my turbo and tail pipe other than the factory EVBP valve for startup. I get smoke on any of the tunes if I want but I don't hammer it at 1000rpms and expect it to get up and just fly without it. If you're easy on the throttle (it's easier with a chip to do so) then you won't see so much. The only way to get rid of it is to get everything else up to parr with the tuner and injectors. I'm still waiting for my 38R money to just show up.

 

I went with a Pro-Flo muffler ( it was a freebe ) on my 7.3, it's not noisy at all.. Roll down the windows and it has a growl, and you can really hear the turbo.. Roll the windows up and you really cant hear anything.. My dad has a Magnaflow exhaust on his 05 6.0, and I LOVE the sound of that truck.. Just driving down the road you cant hear anything, get on it and it sounds like a stout V8 gasser.. His smokes quite a bit, no cat.. My F-450 has a stock exhaust ( thinking about dumping it here pretty soon to see if it helps with the crazy EGT's that thing has, I guess the weight to be around 12K, give or take, so it's not really out of the ordinary ), and it smokes just as much... His has a Edge W/ Attitude Platinum, my F-450 has a Edge W/ Attitude, the plain jane model like I have actually has higher power increases ( 290 TQ compared to 250 TQ IIRC ). When you romp on either one, I'd say they smoke the same. Once your in boost neither smoke at all..

Black smoke while not in boost, your never going to get rid of that. It actually helps spool the turbo. I actually tune for more smoke while not in boost because of that. When under boost, if things are right you shouldnt get much smoke.. A lot of guys love the smoke, I'm not one of them. It just gets all over the rockers and the trailers.. My 7.3 smokes like a freight train if you lug it ( far, far worse than the 6.0's ), or your not in boost. If I foot brake it and stall the converter, I can flat make everything behind me disappear ( haven't done that in a very long time ).. If I play with the Edge on it, I can make it smoke while in boost, but it doesnt run any better. When in boost there is next to no smoke at all.. The guys that are blowing smoke at 20 PSI are tossing performance and fuel away.. Although you could argue that it helps lower EGT's ( I have seen this with 6.0's, but not 7.3's ).. On the flip side of that, smoke and a 6.0 dont go well together, unless you like cleaning turbo vanes..