Cruising RPM jumps?

whatsup. Well i have a '92 gp se 3.1L V6 and just recently my cars been acting funny. I took it to the shop and they diagnosed it by computer that i needed a new fuel regulator and my number 6 plug was fouled. I got a new fuel regulator and changed all 6 spark plugs. My car runs but when im at like 35+ and let it just cruise and give no gas the rpms fall a little bit and then jump almost like it doesnt want me to slow down. Does anyone know what could cause this?

I figured out that the guy who fixed my car only slid one vacuum hose halfway in the intake. I pushed it all the way up and it fixed it.