Weird thing with Carburetor Rebuild. You seen this before?

[velocityboy]

So the truck suddenly started having a bad idle and hard start probs. I know I let it sit a while sometimes but even if I fill the bowl manually it still doesn't want to idle. In the past, If/when I got it to warm up it would idle better, but still a little rough. Any on throttle action was perfect though.

I figured there might be something in the idle circuit of the carb and/or bowl draining probs, so I decided to have a go at rebuilding the carb, a StreetDemon 625. Once I got it apart though, I found these weird bubbles in the body of the bowl. They sound crunchy to the touch, but don't flake apart when I touch them. At least not yet anyway. Obviously I'm not thrilled with these...I have half a mind to sand them off smooth just so they don't disintegrate and make it into the rest of the carb system and just finish the rebuild. But I'm also afraid the prob is just going to continue over time. I know these StreetDemons have sort of an iffy reputation anyway, and it's within my means to just go ahead and buy an Edelbrock 650 instead. But also I'm not thrilled w spending $450 basically because of bubbles.
Just wondering what you all think about it. What would you do in my position?

Here's a vid of it too:

 

[Fellro]

It looks to me to be a kind of coating that isn't doing well with gas sitting on it.

 

[velocityboy]

My thoughts exactly too. After I posted those pics I went ahead and took a razor and scour pad to the bowl and a lot more came off in large flakes. Definitely some sort of black colored coating they coat the bowl with. Presumably they do it for a reason...maybe the composite material they use for the bowl doesn't like gas either? In any case I've pretty much decided to go with a professionally rebuilt Edelbrock AVS2. This demon will go into the trash unless the rebuilder wants it.

 

[velocityboy]

While we're on the topic of carbs, does anyone have any thoughts on annular boosters vs straightleg? The options I'm seeing from the rebuilder are either a 650 AVS2 w annular boosters, or a 1406 600 with straight boosters. Both close enough to the same price that my wallet is fine with either one.
I've run the numbers ref what size carb I need for what I use it for (regular street driveability with occasional hauling to the dump), and looks like I should be shooting for 600. But I'm wondering if I'd be fine or better off overall by over carb-ing it a bit with the annular 650 due to the more restricted venturi and theoretically better atomization.