Hi Mr Camster, and welcome to the site.
Is your 98 a SOHC engine? if it is, then I think what your are hearing is the air going through the intake. All SOHC's do this and it only happens on the SOHC engine. My 95 OHV didn't have this problem, but my 97 SOHC does. I talked to a Ford Engineer at the Truckhaven run and they know about it. He said it had to do with the plastic input tube, and they weren't making too much progress with it(read "we are not going to do anything about it"). You get used to it, but at first I took it back to Ford, because I thought something was wrong, and they told me that same thing. "it's normal"
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Happy Wheelin'
Ray L.
97 XLT 4X4 4.0L SOHC
Dead Link Removed
[This message has been edited by Ray Lobato (edited 05-25-2000).]