My thoughts would be to check fuel flow first. This is because of an experience several years ago when I had gone through the system at annual and replaced the fuel hoses. I was very careful to avoid cutting the internal lining of the fuel hoses when working over the barbs and thought I was careful in other areas as well. The test flight after the annual proved me wrong on the careful score. The engine ran well on idle and the run-up was normal, however, after about thirty seconds as I climbed at full throttle, I had a severely rough running engine. I flicked the switch for the aux fuel pump, reduced the throttle to about 4000 and things smoothed out a bit and was able to return to the runway.

What I found is that on tightening the clamps at the fire sleeve ends, I had tightened one sleeve beyond the barb and tight enough that it constricted the fuel line reducing fuel flow. I had sufficient fuel flow for idle and to keep the bowls full at low power, but once at full throttle, the bowls would empty enough that the engine ran rough.

A further note: When evaluating my installation, I pulled all the hoses off one by one and checked them. I discovered that my constriction was very difficult to find as superficially, everything looked fine. It was only by trying to look down the tube against a light that I found one section where the light never became visible.