Which replacement turbo for cat c-12 to get?

Old turbo is getting old and looks like a tiny bit of oil sling out the discharge. Spent all day installing pdi Manifold and Detroit turbo s475 non wastegate. HEard a bunch of hype on these things. Anyhow, i went for a test drive and the truck is now a complete turd till it gets to 1600rpm. LAg like crazy. Its boosts to almost 45 psi but dont feel any increase in power. I cant drive the truck like this for a few days til i get another turbo. The stock turbo is incredible compared to this one. So yeah, i already took the detroit turbo off and it will be for sale. Putting the old one back on in the morning till i can get a new turbo shipped to me this week.
So which one is the best bang for the buck stock wise. Not looking to spend over 700 bucks again. Borg warner? what is the part number? Any ideas if there is a better one than stock? My cat part number on the turbo is OR-7578.
Thanks for your help and insite.

 

truck has 500+ hp tune on it and ran strong with no lag. No boost leaks at all.

Upon further research, looks like the borg warner k31 172743 is the unit i need

 

It’s a done deal brotha. Ordered k31 this morning. Appreciate your post

 

Just an update, and wanted to let you know, I’m very very happy with the k31. Very noticeable difference in power and spools the same if not better than stock. I should add that I also installed pdi big boss manifold. With this wastegate turbo, I went from stock 28 psi to about 34 psi.
Haven’t pulled any long grades you to report on exhaust temps but soon as I do, I will report back

 

im loving it over the stock unit. dam good unit