Part of the pcv system on the efi valve covers is the small hose that runs between the valve cover and the throttle body. It's there to provide metered make up air to the crankcase under high vacuum conditions when the manifold is pulling air from the crankcase through the pcv, and to help vent the crankcase when the engine is under w.o.t. (no manifold vacuum). If you go with standard valve covers, you need to be able to connect the port on the throttle body to the valve cover if you want the pcv system to work as it was designed. As for height, you'll have to compare what you're putting on with your stock covers. Measure the smallest gap between the lowest part of your manifold upper (usually a fitting of some sort on the driver's side or the throttle body linkage on the passenger's side). If you have 1/2" clearance, and your new covers are more than 1/2" taller than your stock ones, then you're gonna have clearance problems. They make 3/8", 1/2" and 1" spacers to go between the upper and lower manifolds - raises the upper allowing it to clear the taller valve covers. Be sure you get the longer upper manifold bolts to go with the spacer if you go that route.
Oh - and if you leave the breathers on it, you'll allow non-metered air into system under high vacuum conditions. May not cause much of a problem, but you should know about it.
