I can testify to this, ive had my rb20 for 7 years on various mods, and never opened it up.
Running a fair wack of boost (19psi), on a large turbo (gt3082r) it makes decent power. Sure its a bit laggy, but as said its made up for when it really picks up speed.
250+rwkw in a 32 is enough to keep up with most repowered rb25's - no problems thrashing 90% of cars from 0-100kph
Even running a rb20de gearbox for the whole duration - its the torque that kills them not speed and since its laggy the box doesn't seem to mind one bit - even with some mid range clutch drops the box doesnt miss a beat.
A lot of people underrate the abilities of the 20, and its cheaper gearbox - but for price in hand, its a good direction to take for those on a budget.
That said, mines on 215,000 and still runs like it was 100,000
3.5k is not enough to make any real amount of power - almost better spending it on styling mods