'75 Blazer Popping throught the carb

[cdvntx]

Hi folks, I'm new here. I hope to get some great networking here.
I just bought a '75 K5 Blazer. I drove it for about a week and it ran great, then it started getting a popping or backfire through the carb. It idles fine. When I blip the throttle hard or run it at 2500rpm and above it starts popping constantly. This is a reman 5.7l with a 1406 Eldelbrock 4bbl.
What I've done:
Replaced timing gears and chain.
New plugs
New cap, rotor and coil.
I've checked the compression. 150psi across the board.
Vacuum reads 15+ inches at idle. At 2500rpm the needle flutters a little.
I looked at it at night and no light show.
I have taken one plug wire off at a time to see if it was a particular cylinder, but it still popped.
Any ideas?

[Cableguy]

Replaced timing gears and chain.

Sorry I'm not sure of your experience but timing might be off when you did the chain? Possible?

[tbplus10]

Sounds like the timing is off, could be only a tooth or two since the truck seems to be running fine otherwise.

[Gmcsuvguy]

Timing is advanced to much.

[cdvntx]

Both mechanical and ignition timing are dead nuts.

[GaryL]

It may be running a little bit lean. Did you replace the fuel filter? Is it the stock jetting for the carb?

[collinsperformance]

is the egr system working correctly? might be plugged or not sealing all the way allowing a lean mix or fuel to exit into exhaust?......mike

[cdvntx]

The #2 exhaust valve is not opening all the way, looks like a bad cam...

[Pete95Sierra]

sounds like an excuse for a bigger better cam

[cdvntx]

You're right. If I can figure out the head and block casting numbers on this re-man motor and size the cam appropriately...