It seems unlikely that all the lifters would bleed down. What ratio are your rocker arms? Factory rockers are 1.5, after market are available in 1.6 and 1.7 allowing the valves to open deeper into the combustion chamber. I would pull a push rod and measure it and then check it against your cam specs. You say that it has alluminum heads, has the block been decked. You may need to contact the manufacturer for advice. I would also talk to an enigine machine shop they should be able to shine some light on this.
