people seem to tink dey get 15 to 20bhp,which isnt true,id say an extra 5to10bhp..but u should deff feel the power increase
there goes the neighbourhood lol...
You'll get a bit of an increase, Watch for boost spikes with the lack of restriction in the exhaust though, you'll get a power gain if this happens, but it won't last long...
Minor gains to be honest, just watch for your MOT depending on where you're based, and i would think 5bhp MAX
a full exhaust will be lucky to get you 10-15...