i have an '01 supercrew 5.4, and i just put flowmasters 40 series recently and as soon as i left the shop when i hit about 40-50 the truck started to strugle to stay at that speed. kind of like it wasnt getting gas or something. i noticed that the problem goes away once the truck warms up but still does it at 40-50 pleas help me!!!

 

loss of torque from the flowmasters

 

check fuel pressure at the rail. id say maybye a plugged cat but ot would be struggling all the time not just 40-50 mph. probably something simple. when was fuel filter changed last??