Noisy vibrating shifter

Last summer I converted my three on the tree to four on the floor. Got everything new from Brewers; everything fit perfectly and works great. Using a B body pistol grip shifter with std rubber boot/bellows. The only thing is, I get a really annoying rattle/noisy vibration when accelerating. It sounds like shaking marbles in a coffee can, and it really bugs me. If I hold the shifter and push it forward or back just a little, it takes up any slack and the noises are tolerable. I've got all the right bushings in on the shifter arms (steel ones, not nylon). Any tips?? I've never lubricated any of it (except of course that the shifter mechanism [Hurst] came pre-lubed--but then it's not the Mechanism that's rattling...).