i was a spannerman ,many years . heres the sort of advice i sometimesdished out -----------
"you say the problem happens only when you pull away ? "
"well,,,,,mmmm,,,, if i was you ,i wouldnt pull away "
<from wot you say,it sounds like it could be anything from a split rubber intake hose to even a dickey valve . best you get it looked at as sure as the sunrise it won"t fix itself !