Edzin

Hi, just acquired Series 3 88"on 90 chassis with 300tdi with auto box, disc brakes on tdi axles. Goes well but brake pedal needs lots of push to see any action, there is some suck at the vacuum tube so looking for best replacement servo. The servo fitted has a 12v spade connector for something ? My research shows a series 3 servo to be STC 1816, so need to decide whether to buy cheapest; about £57 + vat. unless there is a better option ? total newbie to Landyz so any advice is appreciated.