Noises and Belching

[lemec]

I'm coming up on 6k miles, and I've searched and read various things here, but... I'm guessing this is normal. At certain engine speeds (e.g., around 3500 rpm under moderate load, and one other point faster than that, can't remember), I have what sounds like the noise the lifters in my old Miata made from time to time. Higher or lower rpms and the noise goes away. Seems to have developed within the past few k miles. The thing seems to run fine up to red line. It is definitely not pinging or detonation.

Having never owned an oilhead or airhead, is some noise like this normal? Will a good valve adjustment rid this noise, permanently or temporarily, or will some clatter always be heard?

More of a concern is this occasional belch or backfire, which has caused the engine to stall a few times. Not a big deal except the first time it happened, I was merging onto the GW parkway leaving DC in heavy traffic. Downshifted, blipped the throttle, and BLAP -- dead. With the clutch in I restarted as a Chevy Yukon rapidly filled my mirrors -- THIS is a problem. Is this related to that evap cannister?