I just replaced the intake manifold gasket last week and drove it home that night without any problems. After 10 minutes of driving the next day, I start to smell burnt oil in the cab. Problem went away after a few minutes but would return when I slowed down and turned off the truck. Now it smells like gas after about 10 minutes and doesn't go away. Any ideas?

 

Check over all your work.
Take a close look at the rear of the lower intake manifold. Make sure those quick disconnect fuel lines did not get loose. The oil smell is probably just from the disassembly from removing the upper and lower intake. Try to get a small mirror and look and the rear lower intake seal to make sure its installed properly.

 

While looking under the hood today with the engine going, I noticed some white smoke from the rear area near the manifold. Turns out the PCV valve got knocked out and we never caught it. Drove roughly 350 miles before noticing it. Replaced the valve, again (did it three weeks ago), and put it back in. Smell is gone, note to self, look at everything. Thanks for the input.

 

Its the little things that get us...
Glad to hear that u got it fixed.