LY 182
thats not true at all....Will use more petrol because it's dumping a small amount down the exhaust.
unburnt petrol will not ignite in an exhaust system especially not on an n/a car.. you would need the exhaust system super heated before pouring unburnt petrol into it would ignite..
it actually leans the mixture off on overrun... and alters the ignition timing so the spark happens closer to when the exhaust valve is open....
to a point the leaner the mixture the more explosive!
so on that basis no, mpg wont be affected