i was driving my 289 mustang on the other day and a friend who was behind me said he saw "gray smoke" come out of the tail pipes when i would give it gas. i pulled over and why it was idiling it smelt a lot like gas. there was also a liquid coming out of the tail pipes when i would rev it, possibly gas. could the "gray smoke" be gas, and what would that be from? bad spark plug? please help thanks.

 

generally fuel smoke is black, oil is bluish grey, and water vapor is grey/white. Hard to know without actually seeing your car, hope this helps some.