Problems with chevy astro 90 4.3L 6 cylinder?

i have changed 6 spark plugs, bosch plat, changed motor oil,filter, and added an upgraded air filter, K&N, my astro hesitated when going 30mph and higher,or even sometimes, when i stop and go, then in a couple of minutes, the service engine soon lights come up, can anyone please help, im also trying to upgraded parts too, and im just thinking about buying a turbo