Assuming the plugs are good, you didn't change anything electrical, bump an elec. connection somewhere, (voe), and it's not leaking fuel, I'd suspect a lack of fuel. A fuel pressure and volume test could eliminate the pump as a cause. Checking and or changing filters, starting with the last chance banjo fittings on top of the float bowls all the way back to the tank is always a good idea. If you think it may be just a mixture problem, while it's struggling to go up a hill, gradually add some choke and see if it improves.