There are several reasons why new, fully rebuilt, or good used turbos leak oil, having nothing to do with a turbo problem:
These are the top two reasons why new, rebuilt, or good used turbos leak oil on custom installations. There are two other less common problems in this area:
You will not need to have your turbo re-balanced if the following applies:
If you have a T3/T4hybrid turbo, there are four different styles available:
The only way to determine which size shaft you have (without taking the turbo apart) is by the size of the compressor end nut. If your turbo has an 11mm (7/16") end nut then it is a big shaft version, and if you have a 10mm (3/8") end nut then it is the standard shaft version. There is no way of determining which type of thrust bearing you have without disassembling the turbo to see.
Here is a pretty complete list of items you will need to purchase in order to install a turbo on your non-turbocharged vehicle. There could be a few more small things such as nuts, bolts, fuel lines, etc. You will not need an intercooler if you do not plan on running more than 10psi of boost.