3406E "stock" turbo 475 HP

Happy new year to all!! I want to replace the turbo on my Pete, 520,000 miles with a 3406E 1lw (I think), I did check my vin # at pete and it is what I remembered OR 7223. I know the B/W # is 177148, but I'm wondering if I can do any better? I have looked at posts all day and I just cant find anything about better performance at 475 horse, everything seems to be how to make 700 + . I am pretty happy with what I have, but it would be great to spool up a little faster, and of course mpg is more important every day (hope and change). maybe the b/w 177148 will be a little better. A couple other numbers I looked at 174260, 372 - 500 HP I thought this might work well, but not having housing sizes, It may be to tight on the exhaust side. I think the other one was 174169, probably way to big. I would be ok with a little tighter exahust and no waste gate, as I am the only one in the truck, and I do know how to let off the pedal.
If Mr Haney happens by here thank you for all your info, all the time, but double for your answer to Markvfl a couple weeks ago, more real world information in that one post than anything else I've seen.

 

Yea, that low nox thing. I just don't know, I do most work myself, so not much shop time, only twice I can think of, about 4 years ago injector cups # a KW shop, so probably no flash, and about 6 years ago I had some work done # Cat, we talked about flashing to 550 but didn't do it, so I think it is the original flash.
So how do I find out? I can get on a generic computer box at a lease shop, but I don't know what to look for, maybe can't even get that far, I'm not sure.

 

This is where my knowledge stops how do you find this interlock code? as I said I only have access to a somewhat generic computer box. if I can get far enough will it say "interlock code"?

 

Underpsi, I never answered the second part of your answer/question.
The reason I am replacing the turbo is insurance, several people with the company I am leased to have blown turbo's in the last year and they have had to pay premium to replace them, I checked at Pete and my turbo was $2200, for me it's worth $1000 to have one on the shelf. I also have to consider that when we are busy, one day may cost me a thousand in revenue, so I can't go hunting then. I was lucky to find the Borg Warner very reasonable, now I think I will put it on and then put bearings and seals in the cat unit for the spare.

One more question if anyone knows about the B/W 177148, there is a groove cut around the inside of the compressor housing about a quarter inch below the top of the wheel, I have never seen that before, I assume it lets a little air into the secondary fins, or maybe for harmonics? Just wondering.