From the description of the problem, I would suspect that the technician has accidentally installed the timing belt a tooth or 2 off from where it belongs. This would result in a dramatic power loss, rough idle/ stalling at idle (especially under load such as when the compressor comes on). The most important clue is that it had normal power when brought in for the maintenance.
I would suggest contacting the manager of the shop that performed the timing belt replacement and make him aware that the power loss was not there before bringing it in, and ask if they will double check their work at no charge to make sure that the engine is in time; most shops would readily agree to do so.
If they refuse, then take it to another reputable shop and make them aware of the history of the problem; the Honda dealer would be even better as their diagnosis may hold more credibility. If they find the timing belt installation to be the source of teh problems you describe, make sure they document it in writing and then present the bill to the original shop for reimbursement. If they performed an incorrect repair and refuse to correct the problem when given an opportunity, and the incorrect repair is confirmed and documented by the dealer, I would suspect you would have an excellent chance of obtaining reimbursement in small claims court.
But, again; give them the chance to double check the cam timing without being threatening or anything. Everyone makes mistakes, and I don't know a tech who has never installed a belt a tooth off accidentally. (Usually you can catch this on a test drive before returning the vehicle to the customer though!)
If they agree to investigate the complaint, I would suggest going for a ride with the service manager before and after the repair to verify that it is indeed fixed.
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