and don't forget that simply shoving more air into it ain't doing anything but maybe clearing up some tailpipe smoke, to a point.
At that point, you have to look at EGT.
It's entirely possible to shove enough air into the engine that EGT goes way high and then you start melting pistons, sinking valves, tulip'ing valves, burning them, head gaskets, taxing an already taxed cooling system, running the transmission hot (and remember a BX ain't got no trans fluid cooler) among many other things.
5 psi is about all you can get away with, safely. Won't even notice 5 psi unless you're at 10,000 feet altitude or more. Then you get to enjoy the benefit.
So a lot of guys start cranking up the boost, which is fairly easy to do. Great. Makes power now. Also great is that it's entirely possible that your compressor is running hot, shoving hot air into the engine, making more egt, reducing power, increasing the engine oil temp, reducing the life of the turbo, etc. Also, non intercooled engines will make power for a little bit but after a while they start blowing hot air which reduces power even more. The original Powerstroke diesels were notorious for this. A long-ish run down the interstate with a load, you noticed a power loss (heat). In '99 they put an intercooler up there, and it was daylight and dark difference (but there were also a ton of other changes too). Intercoolers make a huge difference in that department, but on a BX there's no room for one. There's barely room for an engine on that thing, so you are on your own there.
Last issue is sourcing the parts and then installing. Turbo's come in TONS of variations, so one from a D1005 may be too "big" for yours, or one from a D722 may be too "small". Remember there are differences in the turbine and compressor housings, the wheels, and a ton of other things--and OEM's match the turbocharger TO the application. A generator with a D722-T may run for days/weeks on end at full throttle, great application for a turbo at 5-7 psi with a somewhat "larger" compressor. In a tractor aplication, it may be too little or too big. Probably too little since generators run at 1800-2200 RPM mostly and a BX or mower may run at 3500-3700. Then, May not be enough room between the engine and the lower hood. Run without the lower hood, wouldn't be the first I've seen or heard of it. You're gonna have to figure out the oil drain, may already be a hole in the block for it. Feed is no problem as most of them have a drilled passage already there, just plugged
been there done that, isn't worth the expense if you have to buy all the parts. If it's all free, it's probably worth doing. If you care about the tractor and all the stuff costs money to buy, definitely not worth it. Knock around tractor that you don't care much about? Free parts? By all means go for it!