Rough take off
 

Ok,just wondered if anyone out there has this same trouble. My Chevy 350 in my 78 GMC is a little hesitant when i give it some gas. Noticed this ever since i changed the air filter . Any thoughts to what i might have knocked loose?

Are you using the stock air cleaner or an open air element?

Rough take off
 

Im using the stock air cleaner.

Might not have anything to do with your changing the air cleaner.
With the air cleaner removed and the truck "NOT RUNNING" look to see if you are getting good shots of fuel from the accelerator pump when you open the throttle.
If you are not getting two good squirts of fuel shooting into the primaries below the choke plate as you open the throttle it could mean that you have a bad accelerator pump.

Rough Take off cause
 

Factory quadrajet has an accelerator pump? Thanks. Heath

Yup, it is that rod that sticks out the top of the air horn. On the front of the carb towards the throttle linkage.

Could also be your vacuum advance is bad. Check that also to see if it moves freely.

I would also readjust the mixture screws a bit. Get a vacuum gauge and start on one side. Turn in until engine idles rough and vacuum fluctuates. Start turning out until vacuum reading steadies. Readjust idle speed if need be. Then do the other side. Readjust idle if need be after that as well. I usually go back and forth like this about 4 or 5 times before I am finally happy that my mixture is set.

I've had light-throttle "tip-in" problems in late 70's Chevys several times. They hesitate on light acceleration from a dead stop, but do OK if you hit it kind of hard. I think it's just a slightly clogged transition slot (they are calibrated very lean to start with). I just run a jug of injector cleaner in the gas (I prefer Berryman's, smell it & you'll see why), or sometimes a tank of super Mobil will smooth it up.