BMW 325IC

I have a 1987 BM325ic and it recently developed a problem with not throttling. I took it to the dealer and they said that there is a vacuum leak in the intake manifold and needs a new oxygen sensor and a
tune up, the charge an arm and a leg. So I took the car out and consulted a neighbor who knows a few things (actually a lot) about cars. He tried a few things and figured out that when he disconnects the TBS the car idles fine. He does not think that there is any leak, at least we can not hear anything and he says it does not show the symptoms of a leak. So my question is 1-Have any of you confronted anything like this and do you think the TBS is faulty? 2-How do read the diagnostic codes in this car?
Any help is appreciated
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