I have a 1998 toyota tacoma 2wd pu with a 2.4 eng. The truck has 90,000mi. On it. I gave it a full tune up, including the wires. I replaced both o2 sensors, egr valve, and throtal positioning switch. I also replaced the seals around the injectors, cleaned the intake and throtal body. And it still idles rough. Mind you, the last person who own this truck never gave it a tune up, he just did oil changes every 3,000mi. What can it be?