I had that same exact problem sa Mazda ko before.
The cause turned out to be the following
1) Yung maliit na filter sa loob ng carb may bara na nag jelly form kaya i need to press hard on the gas para hindi mamatay.

2) Vaccuum advancer sira na ang diaphram sa loob kaya erratic idling

The fix
For item 1: pinalinis ko carb then dalawang fuel filter na ginamit ko. Before going to fuel pump and before pumunta sa carb

For item 2: Since wala na ako makita na vaccuum advance na pangpalit. Nag re route na lang ng vaccuum hoses and binarahan na lang yung isang port ng advancer. Then tune the carb again

Before you check this route try mo muna mag carb cleaner baka makuha pa