The E-cam is in no way, even close to being "like" a cobra cam... so I fail to see how you think he'd "essentially have a cobra engine". The Explorer engine runs a lower compression ratio than stock. The E-cam, as reported by cam gurus like Buddy Rawls and Ed Curtis, needs a higher compression engine (in the area of 10:1) to actually work correctly. Many people miss this fact, and it really comes down to using a cam that matches the combo. In this case, the E-303 is NOT a good match.
You basically have a stock engine. Stock bottom end with some bolt on's doesn't mean much. You'd need some new pistons to bump your CR, and deck those heads to shrink the combustion chamber.