Intermittent hard starting issue?

Being that it is an older truck and the parts are mostly inexpensive, I have new near everything in the truck. I did not replace the throttle body, but a mechanic replaced the seals and spring. Not all the time but sometimes when starting the truck, it is hard to start so I give it more gas, sometimes a lot more gas by pumping it. When it starts, I have to continue giving it gas and letting up slowly until I get it to idle. If something goes wrong, I ease off the gas too quickly, it sometimes backfires and doesn't start. I will hear a noise and smell gas. The new fuel injectors are still working throwing gas out until I put the key in the off position. The code says 33, MAP sensor voltage high low vacuum, but it has a new MAP sensor.