Hello and welcome to justanswer.com
So right know the vehicle no longer has a starting problem but does have a missfire when driving? Did the restricted performance warning message come back on?
That is correct, it starts fine, and it's misses at exactly 2800 RPM both driving or in park. The restricted performance, with check engine light red or yellow is illuminated, depends on the mood of the car.
Does either the throttle motor or relay or disconnecting the mass air flow sensor have anything to do with the miss at 2800 RPM?
Not really but since the mass air flow sensor was disconnected it may have fouled the fueling adaptations. Clear all the fault codes and disconnect the negative battery terminal cable for 10 minutes which reset the fuel adaptions.