Effect of adding an extension tube to the 'Stinger'

Observed some RC Nitro car had an extension tube connected to the 'stinger' (exhaust pipe gas exit).  

1) May I know the effect of doing it, more back pressure to fuel chamber and engine?
2) If the effect is minimal, wondering if it's good idea to have a long extension tube redirect the exhausted gas the end of the car pointing backward, i.e. jet engine effect gas blowing backward..., and make the body more clean and bring realism to the car?