Hi sudek, what kind of lightsource do you use? Do you practice any other UVA sensitive process? (You can try with another process and see if it's exposing slow too - if yes, it's the lightsource / not chemistry.) Have you tried another paper? (Cheap Masa paper is very iron-process-friendly, try with another paper too, in order to rule out any problems with paper...) Pt/pd and hours of exposure doesn't seem right to me, especially so for materials like Pictorico... If you're Europe based see for Philips tubes ending with -05 or /05 suffix, these are perfect for UVA sensitive processes. (Output peaks between 360-370nm) Tube codes ending with -05-R or /05-R ending have in-tube reflectors; even better...

P.S. Just for sake of comparison; my standart printing time with POP Pd under UVA tubes and 2mm glass is around 6-8 minutes, and (because of self masking) POP Pd is usually a little slower than develop out Pd.

P.S.2. I don't understand what you mean by pre-wetting the paper? IME, COT 320 doesn't need any kind of special treatment...