OK - Your E-gas, this could be either an air leak in the induction or the throttle body needing a good clean, however, when inspecting the air induction trunking its impossible to tell unless you take it apart so its better to just do the whole job at the same time as cleaning the throttle body.
The butterfly in the throttle body gets gummed up with dirt and oil creating a thick viscous fluid that sticks to the butterfly on throttle closing, the throttle motor opens and closes the butterfly in relation to your throttle input, when closed on decelleration it sticks, as the engine revs fall to tickover levels the throttle motor slightly opens the butterfly to maintain tickover - but because of the sticking it cant do that easilly so it applys more power to the motor which then opens the butterfly a bit too much and has to close the butterfly again - which sticks again - this causes the hunting, Its like a car that wont tickover having to have the throttle applied everytime the engine revs lower to the point of stalling.
The reason for the gum is the AOS - it feeds an oil mist from the oxidised oil in the engine crankcase to the induction system to burn the mist off - this is perfectly normal but this mist does leave some residue over time in the throttle body and impurities in the inducted air stick to this mist and create the sticky gum. ( this usually takes a few years to build up)
To rectify, disconnect the air induction pipes and remove the throttle body (You can clean the body without removing but its a fiddly job, takes longer and you cant be sure you have cleaned all the areas completely)
To clean the throttle body just use brake fluid (but dont splash it on paintwork as it will crinkle the paint and remove it) A good rub will remove the gum and make the throttle body shine- the main part you need to clean is around the butterfly and the surface around the butterfly especially the stepped part of the body where the butterfly sits into. (Its like a door sitting into its jamb)
Reassemble and use a tiny amount of vaseline to lubricate the rubber induction tubing before putting together and securely tigten the clips. (Rubber grease is better but its expensive and not that many people have this stuff lying around so vaseline is a good alternative)
The vaseline will also ensure a good seal between the rubber and the joints
If its the first time you have done this job it will take a few hours
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