[s-cars] S4 hesitates , stumbles at elevation

[George Verbryck]

OK , the car is chipped,  Lehman Stage III if memory serves, stock pressure transducer , samco hoses. Otherwise car is stock with the exception of the coil conversion and spark plugs already mentioned. I have had some problems with vacuum leaks but I replaced and/or clamped all the vacuum hoses I could find a while back. In any case it should be painless enough to let the coil fail slowly/dramatically  making it easier to diagnose. Regards, George