Condition: Low Dipping Idle at startup (Stalls) and upon warm-up Rough low idle

When I unplug the MAP sensor, it idles fine and my Stoich Meter is Right in the middle

The guy I got my car from swapped the 305 for a GM Crate 350.

I figured the MAP sensor was bad, so when I got a replacement, I got one for the 350.

Trouble being, that with the 350 MAP and 305 ECM, the car will not start.

I am going to assume I need to match the ECM and MAP.... sound right?

I also looked into a new ECM from NAPA, but you still have to use your PROM.

I'm assuming putting a 305 PROM into a 350 ECM will not help me at all; True or False?

Lastly, is the MAP sensor really to blame or could it be something else?

Thanks in advance,

Steve C - RI

a MAP sensor is a MAP sensor is a MAP sensor (assuming that we are talking "1 bar" MAP sensors for non-boosted applications). They are not matched to the ECM.

Also, an ECM by the same part number is identical. For example, an 88 TPI ECM is the '165 unit, and it's the same for 305 or 350, the only difference is the PROM inserted into it.

It may be that the MAP sensor you bought is bad. The 305 and 350 map sensor should be the same.