mkIV jetta 2.0 increased oil consumption

my sons 00 jeta w/92000 miles ,that weve had for the last 52000 miles was using 1 qt per 2000 miles all along .now after a timing belt change its oil usage has increased to 1 qt per 600 miles,no smoke or leaking on ground, vc gasket is leaking from what the mechanic found so far ,the mech said that a vc gasket leaking shouldnt go thru that much oil ,now its using 1 qt per 600 miles,thats just way too much oil consumption, where is it all going and why did this increase after a timing belt change is what im trying to find out and if its related at all,the vw/audiindi mech said its not related ,i also checked the tailpipes for residue or blowing soot,and saw nothing on paper,but felt no exhaust back presure with engine  revving engine,only felt exhaust pressure at idle. is that strange or what. i just find it  too coincidentil imo, really frustrating