2000 Tundra 4.7 2wd missing

HI i have a 2000 toyota tundra 4.7 2wd but it will misfire really bad at idle and anything under 2500 rpms but there is no check engine light coming on at all. took it to the dealer ship and they said its the exhaust. I just put new tail pipe on it cause the old dual exhaust rusted off. Before i but just a single pipe on it, it ran like a scolded dog. Also when cold it white smokes heavly. Im thinking it may be the computer. truck has 183,000 any suggestions would be appreciated thanks

 

White smoke = tranny fluid or coolant

 

Highly doubt it's the computer. No check engine light tho? If it's truly misfiring it would set a code....

 

Well that's what stumped me it mis fires on almost all cylinders until u rev it up over 2500 and sometimes will idle just fine then just cut out completely kind of like its flooding its self any ideas ... And yes there is no check engine light on

 

Huh.... pinch the return line, does it get worse?