After sitting for awhile (such as overnight) my blazer starts, but only after cranking on the starter several times for considerable duration. Sounds like a fuel problem, huh? I haven't changed the fuel filter yet, nor have I checked the fuel pressure. How much should the pressure read? During the day it restarts just fine.

But something strange... just recently I notice that the exhaust sounds a lot different. I wonder if a clogged catalytic converter could cause this problem?

Thanks for any advice you can give me!
dbteeitup

First, your extended crank in the mornings is likely due to the fuel pump draining back into the tank overnight, thus requiring re-priming each morning.
Replace the tank unit (pump/sender) and while doing so, closely inspect the harness connectors.
If you haven't already, replace the fuel filter while the system is without pressure.

. Replace fuel filter.

. Replace platinum spark plugs (ACDelco only), if they have not been changed in the last 40,000 miles.

. Turn ignition switch to ON, before trying to start the engine. You should be able to hear the fuel pump run for several seconds. This fully pressurizes the fuel rail, before turning the ignition switch the rest of the way to START.

. Check exhaust for blockage.