cruising at highway speeds at low RPM's, between 1500-2000, i get some missfiring/stuttering. i'm pretty sure my truck still has stock plugs in it at 63k miles, could it be the plugs? maybe injectors? if it could be either, which should i try first? not throwing any codes at this time, before i brought it into the shop for a transmission i was getting a code for "system too lean", but the pcm has been reset since then and the code hasen't come back yet
any help is appreciated guys

 

Go buy a can of maf cleaner about 6 bucks and try that remove the maf sensor and spray the cleaner on it and clean the thin wires