Back some time last year I bought a 1k case of blazer brass 9mm 147gr to have some subsonic ammo on hand for when I got my suppressor.
I shot one box out of my gun to to see where it hit, but that was before I got my suppressor.
A couple months ago I shot a box through my suppressor once I got it, but once done, I noticed my suppressor was like a salt shaker and lots of unburnt powder was coming out of it. I could literally shake it and hear it in there.
Today I had a different suppressor out and tried the ammo through it. I also had my 9mm carbine with a 16in barrel (with a different suppressor on it).
I wanted to test the new suppressor on the pistol, and my older one on the carbine.
I also just happen to have my chrono out and decided to see what velocity I was getting.

I tried the pistol first. It is a 5in 1911 with a threaded barrel.
Velocity was average of 1076fps. The fastest was 1085 and the slowest was 1065.
Everything I find online says these should be 950fps, but I can not find any data on what barrel length was used for the test.

I then tried it through my carbine and got the sonic crack. Definitely not subsonic from a 16in barrel.
Average velocity was 1200fps. Max was 1207 and min was 1191.

Both suppressors had lots of unburnt powder in them. The pistol was the worst and I was shaking it out of it (they are both sealed suppressors that can not be taken apart).
The one on the carbine had lots of white powder residue in it with the unburnt powder.
Never seen white powder residue, only black.

I have shot several other types of ammo through these suppressors and never had any noticeable unburnt powder in them.

Anyone else ever shot this ammo and got the same results?
Or do I possibly have ammo that has a issue?
They seem normal and do not "feel" hot, like they are over pressure, and the primers look fine and are not flattened.
It is just extremely dirty and higher velocity than what I was expecting.

I gave up on Blazer as I had the same results you did.

I have tried a lot of ammo and keep coming back to Super Vel for 9mm subsonic.  Clean and always works as intended, though I don't have any 16" barrels so cannot comment on what it does in those.

The much maligned Freedom / LAX Ammo is pretty good to me too though a second to Super Vel.

What I should do is get into reloading but good 9mm loads are inexpensive enough that its not worth my time to make my own.

For factory subsonic I got good results with Federal American Eagle 147gr and Winchester Super Suppressed 147 gr (black box). Both were quiet and burned clean. I also used Federal Syntech 150gr as well with good results.