So, my truck is a 91.5 which started out as an automatic. The exhaust housing on the turbo was a 21CM non-wastegated housing. It's well known in the Cummins community as 'The Lagmaster'.
Basically, after my tranny swap to the 5 speed, 1st gear you just don't use unless you're crawling. 2nd gear is really first, and it would build no boost. 3rd gear is a pretty long gear and it would smoke like crazy until it built boost, which would happen just before I shifted to 4th. 4th gear would built a good amount of boost, but still really smokey on the bottom end, until the boost built.
The truck was so smokey that I was getting a little worried I'd get pulled over. Even tender driving would net a goodly amount of smoke.
So, I started doing some research. There are many options available for the truck...everything from a $2000 set of twin turbos, to a $1000 new turbo, to a $~350 used turbo off a later model truck, to just swapping out the exhaust housing.
Some trucks had 16CM housings which is known to be good with the auto. Some have 18.5, some 14, and all the later trucks are pretty much 12CM with a wastegate. I think that's pretty much the way it is for all the big three turbo diesels these days.
Anyway, I posted a wanted ad and someone shot back that they had a 12CM with no wastegate can...exactly what I wanted. He recommended wiring or welding the wastegate shut.
Well, $60 later I got the housing in the mail. I popped the wastegate cover off and found the flapper had already been welded shut. Sweet.
Well, the job was pretty much a PITA. You know the deal...lots of really tough exhaust bolts, lots of surface rust...hard to get to stuff.
Anwyay, it took me about 5 hrs to do the whole job, but what a difference.
I still don't use 1st.
2nd will grab about 15psi before it's time to shift.
3rd will peg it almost immediately to about 25 psi
4th and 5th are pretty much the same as 3rd.
My off-boost smoke seems pretty much gone...although she'll still blacken the area with the pedal down.
And EGTs didnt seem to climb at all, which is nice.
I'm guessing mileage will suffer a little, for a little while, as I've noticed it's hard to keep my foot out of it now.
Anyway, mods on the truck now are:
3200RPM Governor spring - This raises the fueling from about 2800 rpm to 3200...lets you rev a little higher, but still within an acceptable range for the engine.
Pump mods - Smoke screw turned out to alleviate some off boost smoke, max fuel screw turned in two or three turns (boosts to about 25 PSI, rather than the stock 18...and I think she's still got a little more in her with the stock sticks)
The A518 Automatic tranny was replaced with the Getrag 360 5 speed, and a new clutch was installed
Turbo housing swapped.
Keldermann air bag system on all 4 corners.
10 inch sub, some nice components and an Alpine head unit with iPod input.
Now if I can just get my AC working again, I'll be a happy camper!
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12.57@104 :O) 
Originally Posted by Subliminal
and you gotta remember it tows a car/truck atleast one way lol it is the fastest ve pump 12v ive ever been in ive driven some mild turned up pumped ve trucks but nothing runs like this truck does stock maybe cuz the injectors are wore out and it just smokes like crazy ahahaha
