Yes I would suspect your springs. I don't have the part number in front of me for the proper springs but I will post them when I get a chance. Those springs with the heads you are using will not give you the performance you should be getting. The E303 cam is suppose to make power to 6000rpm. Those stock springs are only good to like 5500rpm maximum before you run into valve float. Hydraulic roller cams generally require more spring rate then say solid cams. When you install the springs you should intall them at the proper height and calculate your spring rate. With the new springs I am good to about 6500 rpm before I run into valve float problems. The new springs I have are double as opposed to the singles that come on the heads and they are much bigger then the stockers.
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