I had a leak at my cross over tube on my 02 f150 with 5.4.
I replaced the intake with a dorman intake. I replaced the plugs as well. Now my truck wont start at all. Turns over fine and it trys to start but wont. I have tripple checked to make sure everything is hooked up. Please help!

 

If it was running fine before the work, you would have to suspicion the work, some how.
Check fuel pressure, needs about 28lbs. minimum to start.

 

I just in the last 2 months replaced mine but with a Ford OEM one. Check your fuel rails to make sure they are seated properly as well as connectors, check all your vacuum hoses and most importantly on the Dorman model make sure the O ring that came with it is on the large vacuum hose fitting on the back of the manifold. This will leak like a sieve at this location and create vacuum lose if its not installed. They have been known to ship lose in the box and not on the manifold.
Its hard but possible you may have injector or COPS plugs mixed up on adjoining cylinders? Torqued down to spec and in sequence?