Chances are the MPFI relay is messed up (passenger kick panel). Check the grounds under there as well. There are 2.

If the truck has been sitting, it probably has shit fuel in it, and changing spark plugs is only 25% of the ignition. The rest has been sitting just as long, and is just as worn/old. Do a full tune-up, replace the fuel filter, PCV valve, clean the TB and IM, use a fuel system cleaner, and put some fresh gas in it. You can't do a small portion of the job and expect 100%.