During my extended troubleshooting venture on my 99 SD plow trucks with the 5.4l, I suspected a plugged intake so I ordered a new intake manifold set. The Magnum gasket set was totally wrong. Even Ford/Motorcraft seals were wrong. Thanks to a very ingenious parts girl at my local Auto Value we discovered that the intake manifold and throttle body are from the 98 model Triton while the block is a true 99 Triton block. Has anyone else run into this problem? No the intake has never been touched before.

 

The 99' model year was a weird year for the Super Duty as it was the first year for them. You could order a new 99' super duty around March or April of 98', which is early. The 98' F250HD and F350HD were the old body style trucks, which came with the older 5.8l, 7.5l or 7.3l. Production was cut off rather early for the older style 98' HD trucks.

Ford made an F-250LD based off the F-150 platform which was available with the newer modular engines. (5.4l) The F-250LD was only available from 97'-99'. My guess is you got an older intake manifold for the F-150/F-250LD on a new block. Ford probably wanted to use up parts inventory they had on hand.

 

this is a common practice.. in the auto industry ... even in the 1960's and 1970's.

even in the early 1980's owners of Oldsmobile's sued GM.. as there New cars came with Chevrolet engines. without notice.