IS20 from GTI for Turbo Upgrade?
 

Anyone ever hear of someone trying to do this? Obviously none of the flanges will be the same but maybe you could take an IS20 cartridge and put it in a set of R56 housings? I only ask because I'm part of a few GTI groups and lightly used IS20s are in great supply, and I have a spare Cooper S turbo kicking around that I'm not doing anything with and I can't bring myself to just sell it with my stock turbo coming up on 100k miles.

The IS20 off the EA113 was a Borg unit so that would probably have the greatest chance of working how I'm thinking. These are all the IS20 specs:

MK5 Golf GTI 2.0T EA113
Borg Warner
6/6 Blade Cast Compressor Wheel & 11 Blade Turbine Wheel
41 mm Inducer / 54 mm Exducer - Compressor
40 mm Exducer / 45 mm Inducer - Turbine

MK6 Golf GTI 2.0T EA888 Gen 1
IHI
6/6 Blade Cast Compressor Wheel & 8 Blade Turbine Wheel
40.2 mm Inducer / 52.5 mm Exducer - Compressor
41.0 mm Exducer / 45.0 mm Inducer - Turbine

MK6 Jetta GLI 2.0T EA888 Gen 3
Honeywell
6/6 Blade Cast Compressor Wheel & 9 Blade Turbine Wheel
39.0 mm Inducer / 53.7 mm Exducer - Compressor
39.1 mm Exducer / 43.8 mm Inducer - Turbine

MK7 Golf GTI 2.0T EA888 Gen 3
IHI
6/6 Blade Billet Compressor Wheel & 8 Blade Turbine Wheel
42.5 mm Inducer / 54.0 mm Exducer - Compressor
46.8 mm Exducer / 50.4 mm Inducer - Turbine

Our turbo cartridge (center housing) also has two oil and two coolant connections that need to be matched. Your best bet would be to find a scrap unit, disassemble it, then compare it to your spare. Chances are, the conversion costs won't be worth the slight performance gains.

The only way I could see it being worth it is if the IS20 off the Mk5 is using a same/similar cartridge to the JCW or the JCW 42mm upgrade turbo from Borg, and you could just bolt the compressor and exhaust housings onto it no problem. It was just a spitball idea and I was wondering if anyone had tried it.