1992 Buick Roadmaster Fuel system,

Extended start up when cold, after start up engine idles up and down like its not getting steady fuel. Once warmed up (about 3 mins) Put it in gear and it takes off and chugs with lack of power. once it changes gear at 25 mph it steadies out and goes fine until I stop and take off again it has low power, then picks up. Fuel filter has been changed. no help. I thought it was bad gas. Used seafoam and hi test gas, no change. It uses alot of gas for take off and start up. The injectors are shooting gas in rhythm to the problems...once i get going its ok
need to repair myself because of age of car the shop i went to charged me $86.69 for a TBI mounting gasket and said they would find the problem but that the troubleshooting process is labor intensive and it could cost 500-1000 dollars before they figure it out..