Throttle Actuator?

Throttle Actuator?
I recently had the valve body replaced on my 05 SL500 7-speed transmission. Ever since, the smooth shifting and acceleration have been replaced by erratic shifting and slow/delayed response. When I slow down for a stoplight or corner and try to accelerate, the car hesitates to engage and has several times led to dangerous situations. After almost a full second of delayed response (feeling like a lifetime), the car finally bolts dangerously ahead. I'm sure that my moment of panic causes me to press the accelerator harder.

In addition, the car shifts harder and the smooth transition between gears has disappeared. Normal shifting use to happen between 2000 and 2700 RPM (for my driving style), but now shifts prematurely into a higher gear, losing the power curve. This is frustrating.

This amazing car has always given me the performance I needed to get out of tight spots and operate with great confidence. The once immediate response is now sluggish. I have taken the car back to the dealer twice to have the speed sensors reprogrammed, assuming that something within the transmission was at fault.

Now I'm wondering if the problem could be the car's throttle actuator. As I think about this, the engine doesn't respond to my foot's position or pressure on the accelerator; the delay to rev up has put me in harms way several times. When I need to shift down to a lower gear, I have to manually do so as the accelerator doesn't respond to my foot the way it use to. Could this be a misbehaving throttle actuator? If so, why hasn't a malfunction shown up on the dash or on my diagnostics meter?

Any help?