Took 2002 avalon for timing belt change--vehicle is now noisy (wasn't before) and does not transition well at 70 MPH

Too many variables considering a major job was performed. You will need to bring it back to the shop for an inspeciton. It's possible something was not done correctly. If you want a second opinion here is a link to find another shop near you. https://repairpal.com/repair-shops Alex