troubles with timing adjustment...

[hysteria]

so i haven't really adjusted my timing since i turboed the car, but before i did put the turbo on i had set the timing at a fraction below 20 degrees btdc. i went back to re check the timing and adjust the idle the other day because since i have put the turbo on and it has broken in it spins really freely and so the idle of the car has jumped up a bit as a result. so prior to adjusting the timing i made adjustments to the idle screw so that the car would idle at ~800 rpms (reccommended idle for adjusting timing). then i did the necessary things and unplugged tps and when i went to check the timing it was way off, or so it seemed... the car runs great and all but i want to knock the timing back a degree or two to be on the safe side. more than this though i just want to verify that my timing is at the correct place. i know that the timing is at about 20 degrees btdc because that was where it was before i put the turbo on. anyhow so any advice? am i doing something wrong? i'm going to try and do this stuff tonight probably so i can go drive my car and have some fun this weekend. i've been riding my bike lately so i've put the car off for a little while. anyhow thanks for the help.