From reading about all of the problems with the OEM IHI turbos I would spend the money and get a better manufactured turbo. You can find ones that are a bolt on and use the same exhaust, piping but you will need a retune. Google, Bing or the search function on here is your friend but here's what I found in 30 seconds of searching on google.
I've been building and fixing sports cars for a while and I've never really heard good things about IHI turbos. I also own a Supra and we never run IHI turbos. The main ones we run that produce great power and are reliable are. PTE, Garrett, Borg Warner and Mitsubishi are really good turbos and I have a PTE 6766 CIA billet journal bearing turbo pushing my 2jz to 730 whp @28-29 psi on "beast mod", 640whp @22psi mid tune and 560whp @19 psi low boost tune. I've had no problems in 1 1/2 years with daily driving and track days at Road America here in Wisconsin.