1999 Toyota 4Runner Proper spark plugs

Hiya,

My 4runner had its engine light come on. Truck was running rough, seemed like only 5 cylinders were working. Had a diagnostic check done. One spark plug was bad. They changed the plugs, not the wires, but did not use the Toyota brand. The mechanic said they were expensive and put in cheaper ones. Now, when I take off in first gear, and low RPM 2nd, I get an engine shudder, hiccup, shake, whatever you want to call it. It feels like the hiccup you get when you are in to high of gear and to low RPM. I have never had this problem before. Other than that the truck runs fantastic. Your help will be much appreciated. Thanks for your time.
Mark Boychuk