Someone else is going to have to chime in with exact location since you have a SOHC the last 3 I saw were OHV 4.0's.

I bet if you follow the fuel rails atop the injectors you will see it. Probably black plastic cap.

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00 XLT 4WD XCSB 4.0 my new baby
00 XLT 2WD RCSB 5.0 swap in progress.
98 XLT 4WD XCSB 4.0 dead
99 EXPO donor motor for dead one and parts for the others.
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