If it runs well after the initial sputter it is unlikely a fuel pump. You likely have carbon buildup in two places, the throttle body and the pistons. The engines run rich, fouls plugs, its going to build carbon. The carbon deposits absorb fuel, especially in the first few minutes, the engine stalls due to lack of fuel. Dirty throttle and MAF sensor lower engine idle speed and contribute to the stalling.
Buy a can of brake clean and grab an old tooth brush, with the key in the off position open the throttle, part way with the linkage, all the way by your fingers. Spray and scrub away the carbon line on the throttle bore and plate. while you have the brake clean out remove the MAF sensor and spray it out good. You will see two small filaments in the sensor clean them with spray only. It will dry quickly on its own. Dont use carb cleaner or throttle plate cleaner as they have oils that will damage the sensor. Brake clean is the go to spray, cleans well, dries fast, no residue.
You will likely see a change in performce with just that. For the pistons, start running a bottle of techron in every tank. Cheap cases found at costco. Its going to take time to remove piston carbon without pulling the engine apart. EFI services that are used on cars for this will likely damage the exhaust hoses, so run techron.
