SIR WRX needs a new turbo. White smoke blowing out the rear on boost. To much anti-lag action maybe

Curently has VF22 in EJ20 with forgies, reverse manifold, FMIC, port & polish heads, extractors, 3"pipes, autronics, closed deck block, 8.5:1 comp ratio, head studs, high volume fuel pump, STi 6MT, clutch plate rear diff, brembos. Also has nos plumb in but not yet tuned.

Looking for imprezive figures on dyno and 1/4 times and I'm thinking that the turbo and existing injectors (and tune of course) are the stumbling blocks.

Q1. are these turbos direct bolt on to the existing flange and bolt pattern? I searched archives and these items got a good rap:
* FP TD06H-20G (which Balistic has i believe)
* AVO 400l
* GT25R
* GT30
if so, which one would be most suited as straight replacement.

Q2. what about a big turbo like T66 with extenal wastegate, or similar; would this work okay with the 2.0L that has 8.5:1 compression ratio?

I'm not fussed about turbo lag as i'm never in a hurry to get to 60kph on the roads .

Any informed advice and experience would be appreciated.

Cheers

gt30 with 0.63 rear and external gate

HKS GT2835R External gate
HKS GT3037R for full boost round 4500 ...but goes rather hard.

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K.E.R.S!!!1