Truck is hesitating and seems to have a mis when accelerating

What is your question?

just had intake manifold replaced because it blew a hole and was leaking antifreeze. brought truck home and ran like new, the next day let the truck idle for about five minutes and the missing and hesitation started. code reads p174 and other meter read that there was only 20lb fuel pressure. I really cant afford to spend all kinds of money on several different maybes. I know that p174 means lean fuel, I have looked for vac leaks checked all plugs for injectors and cops.....confused