Yes, that is why. The cams contact the rockers before the intake is flat on the head and when you bolt it down you are opening some of the valves. If I remember correctly its the rear that stays above the head before bolted down with the pins in the cams. The PVC spacers are ok but you really don't need them. Congrats for making it to the next step !!

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05 Blu LIM, OME GDE Tbo, wk II 245/75/17, KC Lights, bull bar, 195K H TC
05 Blu Lim, Dayton, GDE HT, 255/75/18 , 210K , H TC
06 Bla Lim, GDE Eco, Destination AT 245/75/17, 151K, H TC
06 D Khaki Lim 126K wkII Eur TC
05 D khaki Lim 145k refurbishing
All CRDS: Fumoto, Lift , Fan Shroud mod, fuel head Gen II, SAMCOS,self TB, 2 Mic filt, Hayden