spark plugs and fuel comsumption

Do the different brands/types of spark plugs really affect fuel consumption that is noticeable?

fitted NGK about 1000 miles ago and many people said they give better mpgs but found it the same as the champions...

anyone found a difference?

Not really, the 4.0L is pretty optimized out of the box as to what runs well, the biggest detriment to milage is tire pressure. I run my BFG/AT KO's around 40psi.
The next biggest is the safari rack.