Well if this helps any...
On my 99 Sonata (v6...not that it matters) I tried the same thing, with
the impact wrench- didn't work. I ended up trying to hold the engine from
turning while I used a breaker bar by putting something through the cam
sprocket to help the old timing belt to help stop the turning- big
mistake. DON'T do it by putting something in the cam like I did- it
Anyway, on to your problem... I ended up using a breaker bar and a piece
of wood and a large screw driver to jam against the pully and the end in
the wheelwell (to stop it from turning) and then cranked the bolt off. By
the way, mine was standard thread out (lefty loosy, righty tighty)... so
counter clockwise out.
It was as if the bolt was coroded to the pully (may be that's just our
weather in WI though)