For the same kind of gain you could get a AUDI B8.5 CHRA from Melett and a Turbine housing from China 06H145702Q.
Like that you upgrade your IHI G6 GTI to a IHI Audi B8.5. You just keep your Compressor housing, the compressor wheel of the G6 GTI and AUDI B8.5 are the same.
This is 200% plug and play
The Audi B 8.5 as a IIHI JH5 with a bigger A/R than G6 GTI and a turbine that is 44mm exducer and 52mm inducer Mixed flow. Bigger than a KO4.
G6 GTI turbine is 41mm exducer/45mm inducer
A few guys proof that this give at least 25 WHP more. with a forge wastegate and 2psi more craving pressure you should be at 35 HP more.
You can also compare on APR B8.5 vs G6 GTI stage 2
https://www.turborebuild.co.uk/webs...IHI-RHF5-JH5-06H145702Q-AudiSeat-20-TFSI.htmlhttps://www.aliexpress.com/item/33058011165.htmlhttps://www.turborebuild.co.uk/webs...heel-RHF5-Turbo-5244-fits-JH5-06H145702Q.htmlThe turbine I just put it as a proof of the size. You don't need it as you will already get that with the CHRA.
This will cost you about 250 Dollar
PS: I got build one like that but I also got my compressor housing milled to fit a AUDI C7 RS7 IHI JH5 ( same name)billet wheel 44mm inducer/58mm exducer extended tip 62mm.
With only 18.5 psi at 5800rpm I get 278G/S.
I guess my tuner will manage close to 290G/S with a bit more boost.