Poor Performance

We purchased this range a year ago for our house at 9000 feet. I called Jenn-Air to make sure they would recommend this range at our altitude as they do not, unlike other manufacturers, offer a high-altitude option. They highly recommended it and said the installer could make any modifications. We have had nothing but trouble with this range. Although some of the problems may have been linked to a malfunctioning gas regulator in the house, since replacing that plus replacing the range regulator, we still have these problems: 1) When using a griddle or large sauce pans, the other burner igniters constantly click sensing low gas flow, we believe. If I turn up the burners under the griddle high enough to stop the igniters, the food on the griddle burns. Jenn-Air service center response was to use smaller pans. 2) The convection oven has +/- temperature swings over 50 degrees at times, and has hot spots. A pan of cookies will be half-cooked in the back, and over-cooked in the front. It is worse than a radiant oven. Nothing can be baked in the lower third of the oven.