What was found
(CAN) WHILE CLIMBING THROUGH FLT LEVEL 290 , NR 2 ENGINE POWER WENT DOWN TO IDLE POWER ONLY. ABNORMAL CHECK LIST CARRIED OUT WITH NO SUCCESS. A/C RETURNED TO YMX. NO THROTTLE RESPONSE AT ALL. MAINT REPLACED THE FUEL FLOW REGULATOR IN ACCORDANCE WITH MM. FOUND TO BE SERVICEABLE. VERIFICATION FLT CARRIED OUT&POWER WENT TO IDLE PAST FLT LEVEL 240 AND EVERYTHING WENT BACK TO NORMAL WHEN POWER APPLIED AT FLT LEVEL 180. AFTER INSPECTION, MAINT FOUND ALTITUDE SWITCH NOT WITHIN LIMIT WITH TEST NR 1 AND REPLACED IT