Rpm's Up And Down / Stalling, When Hot

My Villager needs help. First thing in the morning it's fine until about 10 miles or so. Once warm/hot, the rpm's go up and down irratically and i lose power. It's often difficult to get started again from the stop. Around sharp corners it will completely stall. At idle it's fine and if in park and i rev the engine, it seems like it wants to backfire. I have replaced the Catalytic Converter, Distributer with cables and the coil. Please advise as i am in dire need to correct this issue.

Check your tps sensor if its 96 and up.