Mazda - Protege :: 1999 - Loses Power Intermittently?

My 1999 Mazda Protegé has the hiccups ...every now and then it loses power for a fraction of a second. It lasts just long enough to feel it clearly, but it's gone before I can think about it. Very distinct sensation, but it certainly doesn't push me against the seat belt. It's been doing this for over a year (about 5-7,000 miles). No Check Engine Light has appeared at any time. The timing belt was replaced a few thousand miles back.

Yes, I've had it to a mechanic, a trusted local one. I even left it with him for several days. The car won't hiccup for him. I sometimes notice it around town, but I notice it more when driving on the highway (which has probably been over half my mileage in the past year), but I'm still disappointed that it won't do it for him. He suspects a spark plug wire -- he says it's probably only one cylinder based on my description -- but doesn't want to start replacing the wires if he can't diagnose it.

Recommendations? Should I just replace the wires and figure if that doesn't do it, it's part of the cost of diagnosis? (This much I should be able to do myself.) Should I try something else? Actually, as I think about it, he could have been encouraging me to replace the wires myself.