infiniti QX4 2001 - Shudders/hiccups twice durring 2 hr hwy trip

And it gets horrible gas mileage during that 2 hour (~130 mile) highway miles road trip. little less than 3/4 tank of gas or probably 10-12 miles to gallon.
Just recently (2 weeks ago) had all engine belts replaced. Spent most of the time prior to highway trip driving around town (stop and go) and not noticing any shutter/stutters/hiccups etc..
What should i be looking for ?
apologies for CP but nissan group is little slow and light.
Thanks for any helpful advice. robb
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robb wrote:

Hi. No CEL(check engine light0 on the dash? Maybe loose spark plug wire or module? Changed timing belt? then idler pulley? Bad tankful of gasoline?..........
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Too much pie at the truck stop? ;-)
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