Don't waste your time with a VF52 sidegrade...

And what's with all the 18g suggestions? It's a 2.5? it will spool a 20g rear housing fine!?

I'd be, and I did go with a TD06 20G on my EJ255... It didn't make huge numbers(~277hp) as the only supporting mods were 3" exhaust and intake. With your supporting mods plus a walbro pump and injectors(I would just decap, but RT won't do that) I would think it would be pretty close to, if not over 300hp, and should be fairly reliable.
Otherwise the TD05 20G will be a touch more responsive, but without quite as much top end. Full boost should be 4000-4500rpm I'd imagine, and it will still make plenty of power from 3000rpm+

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'04 E46 S/C M3 Coupe