Intake boots don't line up

[Shaughn]

... I have never had luck with impact drivers anyways.

You need to preload the impact driver for it to work smoothly. It's simply a cam ramp inside, and if you don't preload it so the cam slides are in contact, it gets sloppy. Set the bit into the screw(tap in if need be), twist the handle until the load is tight (not pushing in) and then whack it solidly, striking through the driver (like hitting through a baseball). It takes surprisingly little force, and is wicked satisfying after you've been swearing at that screw. If you don't preload, all you're doing is compressing the spring with out engaging the cam until too far down the stroke to be effective. Fully engaged, you're only getting about 20degrees of rotation from the driver, so failing to preload wastes almost all of the rotational force.

Of course, I had my battery box already removed, so I could actually swing the hammer, which I can't imagine is reasonable otherwise.
The replacement allen heads are definately the way to go. Look up robertbarr's page for a kit if you're already ordering his o-rings