Engine "lopes" or lurches at idle and at 40mph on 1999 GMC Yukon

5.7l Vortec. 200k miles. New fuel injectors. Will changing CMP sensor solve this problem?...perhaps? Getting terrible mileage for 4wd XLT Yukon. Any suggestions on getting better out of this engine?

Asked by for the 1999 GMC Yukon
How about a tune up ( distributor cap and rotor spark plug wires and spark plugs )
Just did full tune up. New wires plus distb & rotor get code P1345 so pretty sure it is sensor...trying to see what the field thinks. TY