95 cutlass supreme 3.1 code 75

have problem with hard start every once in awhile, after driving and hot. does not happen all the time. some times i get smell like rotten eggs after driving, pulled code 75 egr valve 1 problem. I have removed egr valve and cleaned. any advise would be helpfull. code has not come back since i cleaned egr valve still have hard start every once in awhile. sometime engine runs up about 1500 rmp's after start up, and slowly comes back down to normal idle. most of the time the car runs good

The rotten eggs smell makes me wanna say blocked catalytic converter. But Thats just a guess.