Simple things first. Go to your favorite auto parts store and buy 2 containers of Complete Fuel System Cleaner. I have used both Slick 50 and Valvoline which both worked great. In some stores it is difficult to find but look for one that is at least $10. Dump both in and fill up the tank with top-tier premium. Before you go start changing expensive stuff, try this.
My friend had a Cadillac that did the same thing. The dealer changed plugs, wires, distributor caps and even the computer. Nothing worked and the problem continued. So one day I am riding with him (I sold real estate at the time) and he asked me what I thought he should do. I told him I thought we should drive right over to an auto parts store where I double dosed the Caddy. Within a few days it was running better. He was amazed, the dealer was probably *BLEEP*ed.
Simple (and cheap)things first.