TCC solenoid failure possible

Slight buck/stumble when trying to cruise along at highway speeds. When it's under load or out of overdrive it does not do it. We have changed plugs, cleaned throttle body, and the car is generally very well maintained (it got it's second timing belt at 125,000 and it is at 155,000 now). Injectors all replaced at some point but not recently. No codes stored.
Started going through 'cheap' fixes to try to find the issue. I replaced the TPS and that was not it. We also replaced the MAP sensor and that did not solve the issue. The only other thought I had was the TCC solenoid but I am not sure if the solenoid can even cause this symptom. I would think the only way this stuttering would happen is if the solenoid is 'leaky', but to me it seems like it should be an on or off situation for the valve. Maybe there's buildup inside the TCC solenoid valve? Is that even possible? Thanks in advance!