When this customer brought this vehicle in for engine diagnostics, it would barley run. Customer stated that another shop replaced his Throttle Position Sensor and electronic Control Module. (Engine computer). He stated that he tried to diagnose the problem himself but could not figure it out. We scanned his ecm but there were no codes stored in his engine computer. the engine at idle would surge up and down and ran rough as if it were misfiring. the first thing we notice was that the spark plug wires were original equipment manufacturer wires. this car is a 1992 and still had original spark plug wires on it. we checked the spark plugs closest to the radiator support because we did not have access to the other plugs which are located underneath the intake manifold. The plugs were excessively worn down. But that still did not answer why the engine rpm's was surging up and down and backfiring under a load. We then performed a smoke test on the intake system. we found smoke coming out of the lower intake manifold gaskets. We then informed the customer of what we found on from our diagnosis. we recommended the intake manifold gasket replacement and the spark plug and spark plug wire replacement at the same time as we would then have access to the other wires and plugs once the intake manifold was removed. He approved our recommendations and told us to replace the gaskets and plugs and wires. Once we completed the repairs, the engine ran great. No more misfiring, backfiring, and engine surging up and down. We also told the customer that we cleaned his Mass Air Flow Meter and that he may be needing to replace his old MAF sensor soon. He said that he would do that himself. We road tested the vehicle and the car ran great on the road test and back. So I don't understand why the customer gave us such a low score. The customer picked up his vehicle and it ran great we he left. If the vehicle was not repaired, why didn't he give us a call to let us know? If I was a customer and paid for repairs, and I felt the vehicle was not running right, I would have made a phone call to the shop as soon as possible.!