99 a-6 quattro
 

p1136,p1138,p1476, had purge fault when initial mil. 3 months these keep returning one scanner says vacuum faults , one says fuel ratio error. I changed all my vacuum lines on manifold and back valves = none leaking. I smoke tested at gas tank and fuel psi. regulator = nothing. the other day light was not on 120 miles but p1136 and p1138 were back in system. the exhaust had a leak a shop removed resonator = no cure. o/2c sensors pass atcon scanner test. I watched them cycle also. :confused: michael