I actually DIY mine and had help with the kanto talyer. Shaking was reduced to almost zero and the rpm stopped becoming erratic.
Eto po ginawa ko.
1. Linis air intake tube. It's the big pipe/rubber tube from the MAF (yung me electrical wires from the air filter box) to the throttle body. Linis mo na rin yung small vacuum tube attached to this. If you see signs of cracks or loose ends (luma na kasi, rubber pa yan) then replace it. Meron sa Mazford Banawe mga 750 pesos. Libre install pa.

Yung small vacuum tube mga 250 pesos.
2. Linis MAF (ingat baka masira), throttle body at replace air filter.Use spray type cleaners which leave no residue (pwede carb-choke cleaner. never tartan or wd40!!!!). If you have the money, have a talyer clean the servo. Except for the servo, madali lang yung MAF (spray do not touch masisira) at throttle body cleaning (spray and wipe lang). In fact naayos ko akin without having the servo cleaned.
3. Clean with contact cleaner (wd40) the distributor rotor and distributor cap (both are at the end of the hi-tension wires from the spark/engine). If cracked or loose, then replace the distributor (or ignition) rotor. Sama mo na distributor cap. Distributor rotor meron sa Golden Isuzu-Mazda sa Pasay-Edsa malapit sa MRT. Distributor rotor mga 850 pesos. Cap ata 450.
4. Replace the hi-tension wire and sparks. Normally naman you replace these from within 2 years.
5. This part pinagawa ko sa talyer. Kung matagal na ginagamit mo yung kotse na nanginginig baka damaged na ang engine support. Have a talyer replace those (di ko kasi alam paano).
Pag tapos na lahat at hindi na erratic idling mo then you now can clean the engine using a carb cleaner (read instruction nuon). After all bumili ka na rin lang nito to clean the MAF and throttle body might as well use it para sa loob ng engine malinis din.
If you are not up to DIY then go to KIA Pasay.
KIA Pasay - from EDSA going to Roxas you use the over pass turning left. The casa I believe is on the left after the cemetery. Paki check na lang.