[Orlando_87GN]

The factory ECM isn't going to support manual shifting. The Buick motor and supporting electronics were designed to be at WOT, not rowing the gears. Things like power enrichment mode, fueling and timing would be real screwed up when trying to shift. Skip all of that and I am sure a dfi at a major expense would take care of that problem. Then with the dfi you lose the drivability you were looking for with the factory computer.

Then there is the tiny thrust bearing in the engine that isn't going to tolerate a stick shift.

You also have to remember that these motors are more resilient than one might think they should be, mainly because they only came with automatic transmissions. Power transfer is fluid and smooth. A manual shift is much harder on all the parts. I don't know anyone with a production V6 with a stick shift behind it making decent horsepower in a regular weight car. If they drove it hard I am sure something would blow up in short order.

Sorry to sound so bleak but I just wanted to share my opinion!