But, I do recall the thing will not fly very well on one engine, unless you're
relatively light, and you're close to sea level. (Turbo charging helps, but it's not a cure-all.)
You obviously don't understand the fundamentals behind turbo charged aviation engines. Its not like your turbo charged road car that uses it for faster acceleration or a truck for more power to haul a larger load! It gives the engine between 10 and 50 more ponies than a standard IO-540, but that is not the main purpose of the turbo charger.
The TSIO-540 has a density controller on the manifold. As you climb higher the density controller senses less pressure in the air mass and allows more 'boost' from the turbo charger into the inlet manifold of the engine allowing greater performance at higher altitude. This is why you can maintain 31" all the way to your cruising altitude in a PA31 whereas a non turbo charged engine will be well below 20" by 10,000.
As a rule of thumb you need 1000m at 40 degrees, MTOW, 5000 pressure height with a 5knot tail wind for take off and about 800m for landing.
When I flew these aircraft I would have a figure for worst case scenario. If the conditions were better than the day and I was at MTOW or less then I was good to go.
And yes the are very poor on one engine. Definitely not for the stupid or inexperienced!