My wife's car starts to bog as though it is going to shut off (never really let it get that bad, I usually turn the a/c off before that point).

I am wondering, what exactly could be causing this? We just took the car to the Honda Dealership about 5 months ago for an entire tune-up which consisted of changing out the water pump and timing belt and all other cam seals and what not.

Can anyone think of anything in particular that could be causing the bogging to occur whenever we leave/use the a/c on for at least 10-15 minutes?