You say you’ve had in the hands of 3 different people. Other than the minor little service items you listed what have these people done? Checked fuel pressure? Check plugs & wires? (Are those the original plugs? What does the owner’s manual say about the service interval on them?). Clean the MAF sensor? Check for vacuum leaks? Is or has the check engine light been on? Have error codes ever been pulled and, if so, what were they? Has anyone ever put it on scantool too check out things like the fuel trim?
In short, provide all of the info to have about past diagnostics and about the car’s maintenance history or the answer could just be “anything could be wrong.” At this point I am going to assume that the Jiffy Lube incident is a coincidence and unrelated.