Poor CNC Machine Finish

I don't know if this is the correct forum but thought i would give it
a shot. I am new to the forum and am the owner of a republic lagun
machining center that I purchased at an Auction it is a 96 with about
8k hours on it. I set the machine up myself leveled it using a
starret 12 inch precision level, put an indicator in spindle and ran
across table to check for levelness and adjusted the lag on the axis
motors all by the manual. After doing all this i still get a poor
surface finish which looks like chatter and i know for a fact the
machine is capable of better because i have a few machined parts that
where with the machine when i got it. With all this in mind i have
determined it must have to do with my setup of the machine and am
wondering what else i could try and or what I am neglecting to do.

thanks alot,

bryant