Need some Help

I have a 1999 Burban 454 (7.4) and I have some problems. First the fuel pump went out. I changed it and pressure is still little low about 50psi. It seems to run fine. Before the pump went out it would start hard sometimes and a little puff or grey smoke out the pipes. I bought a fuel pressure reg and I still need to change it. It is under the upper intake right? Do I need to drain the coolant?

Problem #2 I keep getting a EGR code # 1404 my scanner says closed egr valve position. Now this bad boy is 219.00 at Napa. I pulled it off and cleaned it. It was not that carboned up. Still throwing the code every once in a while. If I drive it all day it will come on and stay on till I clear it maybe once or twice. I used to get 14 mpg on hiway not 10 mpg. The old beast has 146,000 miles on her. I did a True GM tune up at 85,000 miles. Where do I go?????

You need to get the fuel pressure up to 55/62 lbs.
What kind of fuel pump did you use?
Make sure the pump is putting out full pressure.
Block off return line or check direct fuel pressure at fuel filter.

The EGR code is a stuck closed code.
But is not a true code for no open.

You need a engine capable scanner to test it and read out desired and actual position and run the egr testing with a scanner.
Also Check intake and exhaust for restriction ports where egr bolts on.

You should be able to get top cover off intake without draing coolant.