2010 Chevy Impala has a hesitation or “Slip Feeling” at Steady Speed, Transmission Rebuilt

Hey everyone,

I have a 2010 Chevy Impala with 140k miles. Lately I notice a slight stutter or hesitation at steady speeds around 60 to 65 mph, especially uphill. Sometimes it even feels like the car is slipping on flat roads.

Details: • RPM needle wiggles slightly but does not flare • Hesitation stops if I give more gas or let off the gas • Issue improves once the car warms up • Gas pedal has always been stiff • Car sometimes sways slightly in wind and there is a wind like noise at speed • Spark plugs likely original at 140k • Transmission rebuilt recently, new fluid, 2500 plus miles on, stall test normal, no slipping • MAP or MAF sensor cleaned with no change • No check engine light

What I suspect: • Worn spark plugs • Weak coil(s) • Possibly dirty throttle body

Has anyone had similar symptoms on a 3.5L or 3.9L Impala? Would you replace plugs first or test coils first? Any other tips or common fixes?

Thanks