Tryed to set the ignition timing.

Have a 1993 2.2L camry. I jumper the required wires, and set the timing to 10 deg at idle. However, the car then does not have enough power to get up a hill. I have to adjust the timing to 21deg at idle in order for the car to operate "ok" with no pinging or roughess.

(thought it still lacks power. Also, on occasion the warning indicator comes on which is a MAP sensor code. When this happens the car becomes very jerky (the power drops and then when you depress the pedal more, it jerks). Has new rotor button, distr cap, leads, and spark plugs. Thought could be cat converter - drilled hole before it and checked pressure - no back pressure at that point. Unscrewed the nipple at the inlet manifold for the MAP sensor - not blocked there (not sure about inside the intake manifold though).

Any ideas?