First, welcome to JF!
I would start by cleaning the throttle body's interior with an aerosol can of throttle body cleaner. After removing the air intake tube, start the engine and while keeping the rpms up spray the cleaner into the throttle body. Direct some of the spray into the Idle Air Control Passage Inlet per the below illustration. Air gets sucked in through that passage inlet at idle to provide all of the engine's air when the butterfly valve is closed (when your foot is not pressing on the accelerator pedal). That Inlet only sucks in air when the butterfly valve is closed so try to get some of the cleaner spray to go into it at idle though it may tend to try to stall the engine. There is a solenoid actuated plunger (the IAC itself) that controls the air flow through that Inlet which is what you're trying to clean by doing this.
By the way, the butterfly valve is that round plate just below the Idle Air Control Passage Inlet that opens when you step on the accelerator pedal or move the throttle linkage.