Toyota Repair: 2000 Celica GTS, variable valve timing, timing chains

Question
I have been on line for days researching information for my mechanic. My son's 2000 Celica GTS 94K was having CEL issues with misfires. Local garages replaced plugs, O2 Sensor before the engine died. Another local garage found that it had low compression in all cylinders. Tore it apart and rebuilt the head (Bent valves). After reassembly we don't have any CEL but we have a engine with severe power loss (hesitation) in the 1000-2500 RPM range. The car has been in the garage ten weeks and he has even tron the engine back apart to double check his work. Same condition upon reassembly. I can't list the components he has checked or cleaned or replaced to no avail. This is driving him crazy and I have a huge bill for a car that won't run right. I always thought Toyota was better than this. Please help!!!!!!!!!!!!!1

Answer
I'm not sure if I can be of much help, can you tell me how the valves got bent? In any case the loss of power may be related to the camshaft/crankshaft timing being incorrect, this engine uses timing chains and variable valve timing and if the timings chains/ sprockets are not lined up exactly as they should be the engine could exhibit a power loss. Just a thought. I also need to know if it's the 1ZZ-FE engine or the 2ZZ-FE, the more information I can have  the more I may be able to help. Let me just ask another question, After the spark plugs and the O2 sensor was replaced did the engine run normally without misfires until the valve problem happened and the engine died?