2002 Renault Megane Problems

Lost attachments to losein

car revs at 3000 when doing 70mph, not much power, is this normal??

the only door that opens everytime with the central locking is the driver door, back left passenger door does not open from outside or inside any suggestions??

Will a towbar from a coupe fit my model

when driving there is a banging noise from the rear of the car

I'm experienceing a 'vacuum cleaner' like noise which happens imternmittently. It goes off wne I brake, sometimes comes on when I turn to the right. Car's been into the garage 3 time where they can find nothing wrong.