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That is weird that you depict MAP as people who refused to help you out, the guys I know there do not seem like they would be like that. Who did you talk to?
Setting the cars hardware problems aside; at times a business should eat parts or labor (even if fault cannot be determined) to maintain or strengthen their reputation. At the end of the day in the performance car world that can make or break a business. You cannot tangibly determine how much money would be lost by not keeping a customer happy, but usually the business will lose out in the end if the bad experience is broadcasted through forums and such.
I can't speak specifics but I work in an environment where reputation is everything, and there are seminars I have been to where they should charts of potential loss of losing one customer over a bad experience could cost hundreds of thousands of dollars respectively.
There are times where we know a customer is 100% wrong, but we meet them at a point where they are satisfied and will be a returning customer. Turning your back and admitting no fault (not sure that it actually happened in this case) is very dumb business practice and nothing good will come of it.
If the oil pump cost $300, they don't replace it (even if fault cannot be determined), the next time the customer wants a $3000 motor built, plus bolt ons and tuning undoubtedly they will go elsewhere; at that point the $300 oil pump is trivial.
My opinion. But again until MAP responds it would be ignorant to put blame on anyone.