Straight gudgeon pin in the 2wd piston is the cause of slap. 4wd piston uses an offset pin so eliminates slap somewhat. If piston to bore clerances are too large then it will still slap. Not sure on the effect of your bore clearances on the slap side of things.

I would ditch the BD10 exhaust cam and use a standard one though. Your lowering the comp so off boost driveability will be slightly worse than normal and made even worse with the BD10 exhaust cam. That cam is generally regarded as useless in a cossie engine due to it making the engine feel somewhat lifeless at the lower end of the rev range, no matter if its inlet or in your case exhuast. Standard exhaust cam is good for 550bhp anyway