i have a vt commodore wagon and i have a problem she starts fine and runs perfect but when it warms up it starts dropping and rising in revs goes down to 300 rpm and up to 1500 rpm on idle it even does this when driving along and then after it does this it back fires and blows the vacumn hose off the bottom of the throttle body then a bit later fuel starts to leak from the purge line from the charcoal cannister if any one has had a problem can someone please tell me