will torque from air impact gun be sufficient for alternator pulley fit?

hi

basically i've just changed the free wheel alternator pulley on my audi a4 tdi familly wagon.
i bought one of the removal tools from fleabay the long splined bit with the multi splined socket/nut. similar to this



got the alternator off then removed the pulley from the alternator with my air impact gun and the multi splined socket/nut. fitted the new one on then ran it down again with the impact gun and the multi splined socket. this is where my problem started, i put the long splined bit down the centre to hold the shaft whislt i tightened the multi splined socket to ensure it was tight enough, but the bloody long bit is the wrong type its a 12 point and i need a long t50 bit by the looks of it

so my question is if i use the same pressure to tighten it up as i did to free the old one off will the torque from the air impact gun be ok as i'd rather not have to fork out for more tools if poss as money is tight

 

More than likley over tightened my 1/2 air impact goes to 296 nm dont know what thread size is on the alternator prob 8 or 10mm the standard bs torque for these is 28nm for 8mm and 56nm for 10mm so def overtightened.