hi, is matching the brands for valve train and cam necessary? for ex. i asked the guy @ skunk2, and he said you hafta use skunk2 valvetrain with a skunk2 cam, i raise the bs flag. i was thinkin bout crower valve train just cuz its cheaper. also, when puttin in a stage 2 cam, are aftermarket valves necessary, or are springs & retainers sufficient?thanks!!