MAP Sensor

Hello. I lent my vehicle to one of my friends and he said that the MAP sensor needed to be changed. I was just wondering, what would a bad MAP sensor cause? what problems would i notice? is it worth changing? does it have anything to do with idle/hesitation? thanks!

Do not even think may be this or that or listen to freinds advice.
Do not start throwing parts at it.
Proper testing is the way to go.
Start with a code check and post back code no.
Check fuel pressure and primary ign system.
How many miles on tune up?

Do not even think may be this or that or listen to freinds advice.
Do not start throwing parts at it.
Proper testing is the way to go.
Start with a code check and post back code no.
Check fuel pressure and primary ign system.
How many miles on tune up?

tune up was done throught the last couple weeks. TB cleaned, spark plugs, fuel filter, air filter, and techron. hesitation and idle/backfire is still there. when i rev the engine, popping noises occur underneath the vehicle (sounds like its coming from the exhaust) when the rpm drops back to idle. when i tap on the gas pedal, RPM drops to 200-300 RPM, then goes back up. actualy did stall once while doing this. no codes, vacuum lines tested and no leaks. fuel pressure is ok. btw, the vehicle has around 127k miles

Ac-delco plugs?
What is fuel pressure readings?
Camshaft retard readings?
Fix that exhaust leak.
Before throwing parts at it get oit on a good engine capable scanner and check things out.
If any past/history or present codes or missfires in history post back
MT