Could be as simple as needing a good tune up including spark plugs, ignition wires, distributor cap, rotor, fuel and air filters.
Fuel Pump
Are you sure of the error code? My reference says it's an unknown, as in non-existent, code
Could be that your fuel pump is losing pressure having to pump the fuel uphill.
Possibly a hole in the exhaust
Your acceleration would depend on various factors such as the steepness of the hill, your speed, and your braking force when riding down. Going uphill, you would likely have a negative acceleration due to gravity and resistance. Once you reach the downhill, your acceleration would become positive as gravity pulls you downwards.
Stay upstream, uphill, and upwind.
I would check the point gap and timing first. If that does not correct it, I would check the carburetor float level.
You can use the delayed acceleration technique when driving on slippery surfaces like ice or snow. By gradually applying power and delaying heavy acceleration, you can help maintain traction and prevent skids. This technique is especially useful when starting from a standstill or when driving uphill on slippery terrain.
If the change happens during acceleration or driving uphill, you may have a vacuum leak.
If it is an automatic transmission going uphill it will downshift to a lower gear for more torque.
Automatic transmissions lose acceleration driving uphill because of the torque converter. The engine turns one side of the torque converter and the other side is splined into the input set of the planetary gears. The torque converter uses fluid to turn the input shaft in the transmission. When the transmission is locked into gear and going uphill the torque converter has to work against power losses from the tires on the road and when the engine is working harder the torque converter cuts or "shears" the fluid and it causes the transmission to overheat. Always make sure you have enough fluid in the transmission
Tom Uphill died in 1962.