I have had fumes drawn back inside on my +4 (2008)on overrun but only with the side screens on (hood down of course), not much but I have noticed it when rolling up to an island and in the 50-30MPH range, above or below that it does not seem to happen or is not noticeable is probably more accurate. Checked everything and no leaks but wise to follow advice to look for petrol stains and do a full spanner check of the exhaust whilst your under there (in fact why not spanner check everything? it all helps)
