l was driving my car when the low pressure light came on i pulled over and got recovered to home sorry a4 b7 2.0tfsi. drained the oil tried cleaning the pick up pipe in sump .she fired up straight away but then at half throttle you could here the chain rattling. would it be just the chain or has damaged been done, i was thinking of getting a new pump  chain and guide,but could it be more serious any info much appreciated thanks 

I don't think you'll know unless you dismantle the engine. It might just have damaged the chain. It sounds like you're handy, so it might be worth carrying on.with your initial plan.