oil overfill and cold run noise

my daughter, away at school, had the oil changed in her 1990 Camaro 305 tbi, auto. The next morning on start up the engine made a loud
clanking-cracking noise, as best as she can describe, louder in reverse, lower in drive and lower still in park,but a clanking-cranking sound.. the noise goes away when the engine warms. The service center denies any wrong doing, naturally, and she took it another service shop and without the engine temp cold they could not find the problem but did find the engine oil was way over filled. This extra oil was removed. There is no obvious damage to the exhaust pipes that can be easily seen. I will not be able to travel for a while and was really curious as to what damage was done by the new trainee at the service center. What can be damaged by overfilling the oil ( double amount on the stick) do?. The fact that the noise changes in different gear makes me believe the exhaust is dislodged but a midas muffler shop could not find the problem . The manual shows a E.F.E. valve (early fuel evaparator) in the left side engine area where the noise appears to be coming from. Can this be damaged?
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