humidity definitely increases the effective octane rating of the fuel.
also, cars usually look and sound better in the rain.

>>
>> On 8-Apr-06, at 9:47 AM, roger sisler wrote:
>>
>>> Hello, my 85 1.9 runs best when the weather gets bad. If it had
>>> knees, I think it could feel this change coming. I have a small
>>> chronic problem with surging engine. Maybe 100 or 150 rpms at at
>>> traffic light.Not much, but it goes away in humid weather or rainy
>>> weather. The engine seems to run better too. Why is this?  Anyone
>>> else have the same?
>>>
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