Vcballer

Hey guys i have a 2003 honda accord, I replaced my starter recently and the intake gasket manifold.
And after i was done my dad forgot to tighten the intake bolts so i had a intake air leak for a day or two.
After tightening them back my transmission started acting up. I don't have any codes that pop up about the transmission from the obd reader, only code is P0420.
But my problem is when it shifts into third gear occasionally it will shift out of gear, and depending on the pressure on the pedal it will rev in rpm and when i let foot of pedal it will shift back into gear.
It will only happen after third gear others it shifts fine into every gear. Also when i start my car in my dash i here a ticking like sound that only happens in park, Brand new problem that popped up after my intake air leak. And it will go away once i move it into reverse, neutral, drive etc...
I dont know if it is related to my shifting problem.
If you guys can please help. I personally don't think it is my transmission, i believe it is something smaller.
Please let me know ur opinion.