Plug wires can cause the "tugging" effect if they are "arcing" in some fashion. They gain resitance as they age. Might as well swap out the plugs as well, and definitely check the electrode gap on the new plugs to make sure they are at spec. Do those two things before you spend the bucks for a full-blown tune-up (although plug wire sets for some models are not cheap)...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car