Problem solved! Checked and cleaned the ICV and checked vacuum lines with no success. ODB came out with a "P0171 System too lean (BANK 1)". With help from a local Ford technician we found out the inlet manifold gasket had a leak, fitted a new one and now shes running great again!
Got myself a 1998 1.7l 16V Puma last year. It was driving nicely until a couple weeks back. Had the MAF sensor replaced because the engine was revving slow, and it fixed the revving problem. Had the ECU reset also in the process.
Since then the engine has been idling rough, fluctuating usually...