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

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?

by in Burlington, VT on March 11, 2014
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2 answers
ANSWER by , March 11, 2014
Check your fuel filter and fuel pump.
ANSWER by , March 12, 2014
scan codes and post if any