ok heres my issue: my truck has 93000 miles, whenever i drive normal my truck seems to bog down ,i watch the rpms drop and the truck start bucking...feels like a miss in spark.....at first i thought it was fuel filter so i changed that....seem to run better but still does it.....whenever i take off overdrive it seems to do it less....with overdrive on and say im going 40 and i give it gas ,sometimes it stays at 1200 rpms and struggles to kick down then it starts its bogging....heres the thing, we ve put several computers on truck and its not reading anycodes, so we created codes to c if computer is working and it is.....heres my question what wont read a code?....a bad plug?....bad fuel pump?....coil pack?.......also my friends 02 lincoln town car seems to have same problem....he said he had tabs on plugs changed (whatever that is)and said it fixed problem for a while but now he has to change all the tabs(what the hell is a tab)......please any help would b appreciated as several mechanics can notfind problem

 

Air filter?

 

What year and engine?

 

its an 06 5.4 motor....air filter is fine.....on the way home tonight its doing also when i floor it....feels like the timing gets retarded and losing power......i wanna know why the computer is seeing whats wrong