After a coil (2) went on my 4.2l i6 the truck won't rev over 3k. No problem driving though, cleaned throttle body ( a few times) pulled fuses to reset also. Since then changed both O2 sensors. Now runs bad a while then good back and forth 3-4 days then switches back. What have I missed? If it was a filter wouldn't it run bad all the time? Also changed alternator about 2 years ago. By the way 200k on the vehicle and transmission rebuilt by some one else 1.5 years ago