I should also add that I checked the duty cycle with the air cleaner off. Does this make a difference to readings? I'm still battling a slight uneven idle. I don't really know what else to check. What is the best way to check for vacuum leaks? The IAC hoses look okay and I've already checked the IAC valve to make sure it was clean. There was no buildup inside and the valve operated freely. I think my next step is to make a code reader and check to see if there are any stored fault codes.

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1989 300CE