I have an 04 6.0. did the coolant filter and recently replaced the egr valve and the turbo valve last year. I have scan gauges to monitor the oil and coolant temps. so I purchased a sct tuner with the canned custom mods, and removed the cat and muffler. Put in a test pipe, put in a piece where the muffler was and and kept the original exhaust. You can really hear the turbine now and i think its a little too loud when i haul or tow. The sct tuner really wakes up the truck. I did mess around with some of the street tunes until i just put it on the tow mode which i usually use, but in the street mode, it is like a race truck. Any suggestions on a muffler that wont restrick the exhaust flow much but quiet this thing down a little? Soounds like my old big block with the flowmasters on it. Also the settings on the tuner. What does locking your converter do for you? when can you safely do it and when cant you? what settings do you guys use for towing? the sct has options for firm shifts and locking the converter in all gears and all kinds of other things. I did turn off the egr valve. what i did notice was when i had some of those options selected my truck would surge and buck from second to third and sometimes third to fourth if the rpms were not exactly right. I ended up leaving the trans options stock and it works fine now. So any suggestions for that portion would be appreciated.

JR