Hello everyone!

So I got an issue with my '90 burb....if the truck sits for a few days I will get about 5-10 minutes of white smoke that smells like gas......after that the smell goes away until you start driving for a while then you get a bad exhaust smell like its running really rich.

Truck specs and new parts:
454 TBI (rebuilt 30K ago)
2wd 3/4 Ton
New Cap & Rotor
New Plug wires
New Plugs
New Exhaust manifolds
New Exhaust gaskets
New Air filter
New Fuel filter
New O2 sensor
new vacuum lines to the Evap canister
New EGR valve --- After this change the truck runs very low idle and lopes...prior to swap it ran smooth but had a really bad odor from exhaust.

So the things I have checked other than the replaced parts:
Checked base timing w/est unplugged- Set for 6 deg. advanced
Checked all vacuum lines
Checked injectors w/timing light - spray pattern is rough but even

So now I am not sure what to look at...... The only other things I can think of are the MAP, IAC and TPS...but not sure. Any help is appreciated.