I'll bet that the problem is a bad fuel pressure regulator. It's leaking past the diaphram and raw fuel is being sucked into the intake, especially when there's a high vacuum (like when coasting/engine-braking to a stop). Rough too-rich-like idle. Hard to start . . . take several seconds of cranking and some push on the pedal to get it to fire, whereas before one turn of the starter and no pedal produced an instant start.
It would also explain the leak-down and the fact that the computer is throwing no codes.
Turn the engine off, then disconnect the vacuum line to the pressure regulator and turn the key on. The fuel pump should come on momentarily until it builds up pressure. At the same time I'll bet there will be a geyser of fuel squirt out of the vacuum connection on the pressure regulator.
A new fuel pressure regulator is about $60, and you have to remove the fuel rail to install it.