Transit 260td 2002?

I have just purchased my first tranny!!! this van is in very good condition and has full service history inclusive of many new parts fuel pump new exhaust new brake pipes all round etc and it has only had one owner with 84000 miles on it. Unfortunately after two weeks it has developed an engine knock which is very cranky.Although this is quite loud at certain low revs there is no problem starting and no problem at high revs on noise but does seem a little underpowered.There is no smoke at any time but just this annoying knocking. On the diagnoistic i have had done the fault reports to a fuel pump fault causing a timing error but i am a little concerned of the expense of renewing the two year old pump when it could be something simple like the fuel filter any advice?

Shakey
October 2011