The mileage above is in Km as I am in South Africa. The brake booster vacuum hose has repeatedly been breaking. It happens randomly sometimes after a few hours and sometimes a few weeks. Sometimes a hole blows in the side of the valve in the middle of the pipe and sometime the pipe just snaps next to the valve. It seems to be caused by a sudden violent rush of air.I tried cable tying the pipe in place and it actually broke the cable tie! I have temporarily used a section of flexible hose in the middle so that when it blows I can fit it on again without buying a new pipe every time. No mechanic here has been able to work out the problem. I have not heard any backfiring noise!
Kind regards - Jonny Blundell. Cape Town SA>