1995 Chevrolet 454 starts then stalls

[J.c.]

I have a 1995 motorhome with a Chevrolet 454 tbi. It was running fine one day and the next it would start then stalls immediately after.  Replaced the fuel pump, filter, map sensor, engine temperature sensor, water temperature sensor, coil and the sensor at the base of the distributor. If I disconnect the vacuum line from the brand new ac delco map sensor it will start and run but not very well. Was told I needed a new tbi system but $500 is a lot of money for me to spend just to find out it wasn't the problem after all.  At the end of my rope and need guidance desperately.  Thanks in advance. 

[M.G]

have you ever figured what was the issue ? i have a 1996 motorhome 454 too im in the same boat been a week trying to figure what could do that i will always start but dies immediatly replace the whole fuel systeme and more and cant get it to run

[Ice1010]

Did either of you figure out what the problem was or is. I have  a 1995 RV with 454 TBI, same problem. Starts right up and then dies, start up and die. Replaced the in-tank fuel pump, no change. Help Help 

[Ice1010]

Did either of you figure out what the problem was or is. I have  a 1995 RV with 454 TBI, same problem. Starts right up and then dies, start up and die. Replaced the in-tank fuel pump, no change. Help Help