Hey
@morgan
There is a bunch of good advice in this thread, and a little misinformation but hey that's the internet for you!
It seems like you have your heart set on buying a turbo rather than upgrading some other parts first and at the end of the day that is your call - you own the car.
If the car were mine I'd first look at one of the intercoolers mentioned previously and then putting an AEM wideband in, upgrading the gearbox, Microsquirt (or some other equivalent, inside the LH2.2 case) + 600cc injectors - and then a decent turbo! You'd have a good 250kw. Actually who are we kidding, if it were my car I would have engine swapped it by now :P
Keep in mind that if you do run a larger (more efficient) turbo, even at the same pressure you will be further from choke point and the charge will be cooler. As a result you will be more likely to lean out, so get a wideband for sure! :)
But let's not get sidetracked by good logic and boringly sensible supporting mods (I rarely am) and look at some of your shiny expensive turbo options!
Considering you are still running LH2.2 and an M46 this really limits the power output to an absolute max of 200kw, So I'll share some research I did when I was trying to get the same power out of my similar B230. Let's be real here and set your rpm limit to 7000, and you're still 8v so we'll go with a VE of .85 (my logs say this is generous but here's to wishful thinking). Add a few other figures and constants, crunch a few numbers and you can sort of plot your engines flow characteristics. Of course, this is wildly influenced by uncontrollable variables (you use your exhaust housing to get your initial VE to decide on a new turbo, then your new turbos' exhaust housing changes that VE - what a stitch up!) and we aren't even taking into account the dynamic nature of VE here. So in short, this is a rough guide at best, pretty pictures at worst. Either way, better than half the conjecture around saying "I reckon x will spool so hard on y" etc.
**** COMPULSORY PRE-READING****
https://www.turbobygarrett.com/turbobygarrett/compressor_maps
So you get the plot and overlay it on a compressor map of your fave turbo - lets try a 16T like the Ebay one you posted;
Here the dark blue line on the overlay is 2000rpm, going up to the orange line at 7000rpm. At a pressure ratio of 2 on the y axis you'll be seeing roughly 14psi on your boost gauge.
And from this we can take home that damn will this baby spool! And it'll sing a sweet song at 4000rpm (centre of the efficiency island), but pretty much anything after 5000rpm will be choked, and the air you'll get will be hot, chopped up and so on.
So maybe you should go up to a 19T?
Yeah look, not a bad street turbo at all - as you can see it has longer legs (broader island)
Want more? let's play with the big boys in XR6T's and bolt on a GTX3582r 3 grand later and then:
Well I'll tell you, you better love revving your engine! But in all fairness, with a smaller hotside and the resulting increase in VE, this isn't a very accurate representation of what it would really be like.
So yeah, to conclude, best turbo for a near stock 8v B230? BorgWarner EFR6758.
But for the $2.5k, you'd be better off going an 18 or 19t and spending the rest on decent supporting mods and a bigger better turbo in the future!
Let me know if you'd like to see some 8v B230 overlays on smaller Garretts or other Holsets, I have them somewhere. And If you go 16V you can change the overlay to suit! But yeah - rough guide only, use at your own risk etc