hey, no not 500rpm,
in terms of rpm there there is not too much difference, i.e say in first gear it will still hit full boost by 3 grand, the difference is in how boost builds..
with a stock cooler car once the turbo starts spooling full boost comes up very quickly, with a big cooler/piping the time between a bit of boost and full boost is longer, so basically is it more throttle response rather than a lot of lag.
my car wouldnt be a perfect example to compare before and after though, as i have adj cam gears, bleed valve and pfc as well which all make the boost come on differently to a stock car.