Followup to this ......

My 97 J30t is very sluggish at times. This never happens when I first start
it, just when it get up to temperature. I have noticed a couple of time
when I take the fuel cap off when nearly empty, it doesn't make the air
pressure noise. Could a bad gas cap cause sluggishness? What else could it
be. I have done new plugs, fuel filter and air filter.

When ths sluggishness starts it seems to be very sluggish from a dead stop
until it hit about 2600 RPMs. And again this never happens when it is cold,
only once warmed up.