Unhappy buyer .What to do ???

Your ad was very clear these were used race parts everyone knows used means used.
And why would anyone who is looking for gear set wait two months to complain.
When I buy parts I inspect them when I recieve them and usally put them pretty quick as they are needed to complete a build.
My feelings are either buyers remorse or they were installed and now he has a problem that he created.
Pretty stand up of you to be this concerned I would buy parts from you based on that alone.