Hmmm. Have to disagree with you, sorry. On my lever pulls I do examine the puck when it comes out, and when there is channeling there is consistent evidence of it, little depressions in the puck surface, like water washed into a sandcrab's hole. Not a hole, mind you; just little depressions, like an inverted nipple. And, its probably a matter of personal taste, but I PREFER the beans on days 1-2... they've always tasted better, to me. They certainly pour different... much thicker and gloppier initially. After about day 5 they tend pour thinner. I make it a point usually to draw a couple cups when the beans are still warm after my roast... yum!
Ben, try using a paperclip (that's what I use, cheap, plentiful, easy to get) to stir your grinds, I do maybe a 15 second stir, sort of a compound motion like the precession of mercury's orbit. Oh, straighten the paperclip first
Then do your tamp. I'd try slightly harder tamp first, to settle your grounds and collapse any voids in your puck which may be contributing to your spritzes. how long does your pour take?
Oh, I do agree with Erik about getting an aftermarket basket. Stay away from the extremes, I use an HQ14 and dose around 19g, but in my Strega that's normal (i.e., kinda big)... start smaller and work up. Avoid the triple baskets for now.