total subfloor thickness should be 1 1/8 inches thick. (as seen on the side of mortar mixing bags. I have also heard wonderboard is BETTER to tile over as the thinset is supposed to adhere better, but it is substantially more expensive than plywood which is used in almost every new home and they dont seem to have any issues...
oh ya, the particle board HAS to go. it has too much flex to it and you will be fixxing cracked grout joints regularly.
C.J.
1997 TSi AWD 2.3L 6 bolt (Carillo Rods, Wiseco pistons, Cometic headgasket, ACL bearings, removed BS, FP3's, Crower springs/retainers, ARP hardware), FIC 950's, Aeromotive AFPR with SS lines, Walbro 255HP, PTE SCM61, Tial wastegate, Greddy Type S BOV, short route FMIC, 3" turbo back, AEM EMS, 3 bar map conversion, BJs SMIM, 75mm TB, Innovate LC-1 Wideband, 18" Focals, Bridgestone Potenza RE040's, Tokiko suspension.