what motor?

If it is the 22RE, it's most likely the EGR letting the gasses in

This occurs when you rev up and get off the throttle, teh engine slows down and EGR gasses go into intake. pretty normal.

did you take off that pipe connecting to the airbox from the radiator support?

 

its the 3.0L. No that pipe is still there.

Its a constant gurgle too, not just when it revs. also it doesnt matter if its hot or cold the noise is always there.

 

Mine has it too but just when i rev up. I thought it was air in the cooling system. It went away for a while when i bled it by parking on a hill and running it with the rad cap off. Maybe im talking about a different gurgle. I had that same noise in my supra too but seemed to be a short time before the hg went. After replaced the noise was gone.

 

maybe you put too much oil on the filter. I had a friend who over oiled a k&n filter and it got all up in the mafs. Just an idea, you said gurgle, like liquid, maybe check that. Those filters aren't worth the hassle in my opinion anyway, I'm an old school paper filter kind of guy, but I don't want to debate about the 1/2 hp you pick up with the k&n