high revs/initial missfire
 

What's up guys I'm new here I've spent a lot of time on this website finding cures for my f150 but I'm totally stumped so I figured it's time to create a profile.
I have a 2000 f150 5.4 Vin L with a refurbished motor that has about 30k on it as of now. Here's my problems.
After the truck sits long enough to cool, and I crank it up and drive it will missfire and idle rough until it gets to operating temperature or I hammer down on the throttle.
Second, every once in a blue moon when I crank my truck, put it in park or neutral it will revv to about 2k rp ms and hold it then dropped down real low and come back up.
What I'm thinking it could be for the first problem is when I was 17 I cut the cats off. All 4, because I was told it will get better gas mileage, so I'm thinking that the no cats are messing with my enabling proper air/fuel mixture until it reaches operating temp. Once it reaches that it runs flawless.

For the second problem I'm thinking it's a vacuum leak or sticky egr. If a vacuum leak any ideas where?

Can I assume that you have a constant CEL with P0420 and P0430 codes because of the lack of cats? If so, see if there are any more codes.