my cylinder 6 is firing at 40 psi i changed the spark plugs coils and wires I plan to check injectors next where should i go after that and is it worth $90 per hour to have some one come through the engine I work on tires for a living so i know my way around nuts and bolts. I just want a second opinion and if my truck has 295000 miles should i just plan on replacing the engine

 

Only you know how well your truck was maintained.
It has some miles on it, but I wouldn't throw in the towel yet.

A compression test would give some idea of the engine condition and you could make a better judgement after you know the condition of the inside of the engine.
A lot will depend on what is found there. If the test shows some life still left in the engine and is pretty even, you might look for another cause.