a few 307 110 hdi problems

[ktnch]

bought a 307 hdi and are having a few problems, when the cars ticking over cold or warm theres a very slight misfire and is more noticeable when you lightly touch the accelerator to get the engine to around 1200 rpm

also the car is surging under acceleration it feels like its been held back then suddenly has a boost and then holds back again, the fuel filter housing was leaking and keep getting messages up saying unblock diesel filter this was only when accelerating on a hill though, i have replaced the fuel filter and stopped the leak around the housing just wasn't tight enough, have not had the warning on from then but cars still surging

any ideas

kev