2000 Volvo S80 Q&A

2000 Volvo S80 Question: After a while the car starts to stop revving and loose power?

It's a 2000 Volvo s80 and when first started runs smooth but won't rev up at all after running for a bit it gets a rough lower idle but will rev up to 1500-2000rpm's and occasionally it will start and run alright for a little while, what's causing this? -
Answer 1
Check your fuel filter and fuel pump. -
Answer 2
scan codes and post if any -