First of welcome.
As for you question.
The RS has a 4cylinder engine (4plugs) Jap version, 210BHP from factory redline 8250-8500RPM
The AS has a 6cylinder engine (6plugs) Jap version of Lexus IS engine 160BHP from factory, Redline 6500RPM
If you stuck up a few pics, Someone will tell you for sure