I read your response, you state "by looking at the invoice..". I keep notes the whole time I am building an engine, as to any problems, things I have doubts/questions about, etc. It is not on a computer, it is hand written, dated, hour of the day, etc. This has saved me alot of problems over the years. If a customer has a problem with something, or thinks he is having a problem with something, or sees something a year later that he thinks is becoming a problem, I can look back at my notes and usually have a good idea what is happening. I am not busting anybody's chops here, just saying that I need more information than their old invoice when I talk to them. You can be 'REAL' sure, if any used parts, supplied by the customer, were involved in my builds, there will be notes to show that and any reccomendations I gave at the time. Hope this all works out. I have always said, "satisfied customers are never heard from, but, one unhappy customer is heard 'round the world".