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Discussion Starter #1 (Edited)
I have just completed the engine swap, putting a 3800SC from what I believe is a 99 Grand Prix GTP into my 97 Bonneville SSE which was normally aspirated. Pretty straight swap from the bolt up perspective. Swapping the flywheel was the only change I made to get it bolted up.

The electronics and the vacuum hoses are a different story. The engine is running and it seems close to right, but just not quite. Actually has stalled a couple of times today when stopped and idling after warm up. This is new behavior after driving about 700 miles on this engine.

Where should the vacuum line from the transmission hook into the system?

The manual BBV I have left plugged into the solenoid because there is vacuum on the line coming from the manual diaphram. I've seen some posts saying to take that line off the solenoid. I don't have a wire on my harness for that solenoid so I plan to leave it unplugged. Should I be able leave the lines on and leave the solenoid unpowered?

Line from the evap canister, should it go all the way across the engine to the solenoid on the back just above the MAP sensor? I ran it back there and the solenoid cycled continually. I swapped the vacuum line from the transmission on there and the cycling stopped. Not sure what to do on that or how it should behave. I thought that solenoid on the back of the new engine was the evap solenoid.

After the car is warm at idle the "Check gauges" light (NOT Check Engine) comes on. I see no gauge indication of a problem. What should I check?

Lastly and perhaps most important, I have read the ECM should be reflashed after this swap. Is this needed? What will it do for me? Can my local GM shop do it? Do I need to explain my engine swap or just ask for ECM flash with Supercharger.
 

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Discussion Starter #2
vacuum lines solve

I have figured out the vacuum routing. That all seems good. I had to add a T to hook the transmission vacuum to port on the throttle body. Transmission shifts much more smoothly now.

Still trying to figure out how to get the ECM reflashed and what to ask for when I find someone to do it.
 
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