Truck Repair: Nissan/Engine Misfire Problem child, valve lifters, vehicle mechanic

Question
Hi, I do hope you have some advice on this prob. For 2 years now, and 5 mechanics later...It began as a #4 cyl. misfire, the truck is misfiring at around 1800-2000 rpms, trips the engine light when I am going about 60mph, and coming down from a hill usually. The last code with the #4 cyl. was ecessive EGR. EGR was replaced-no difference. Decided to swap the fuel injectors--#4 to #1, drove fine for 10 min, then the engine light tripped, coded excessive EGR again. The plugs were changed, about a year old, the #4 plug was cracked. NGK plugs. When all this started 2 yrs. ago, I changed plugs, roter & cap, wires. Through this time the O2 sensor, A/T sensor have also been changed.  I have had some input about possible fixes...crank sensor, coils, vacuum leak, and whatever is hooked to the EGR valve...OOOHHHH wise man, do you have any ideas?  

Answer
Hello Taylor,
You don't give much information about engine size etc, but no matter, I am not much of a foreign vehicle mechanic anyway.
If that engine has solid valve lifters, it may just need the valves adjusted. See what the owners manual says.

Van