Hi, Iv’e a problem with Peugeot 406 2 ltr hesitation etc, there’s
always been a problem with uneven running when under oxygen loop
control upto 3000rpm. Engine is EW RFR type Magneti Marrelli  ECU. A
guy who knows a thing or two about peugeot’s  assured me it was a coil
pack, which I replaced, no better. But stayed with it replacing odd
bits when I had time. Eventually it failed emission tests, so I took
it to main agents, who diagnosed misfire cased by guess what! the coil
pack. Still failed MOT so replaced CAT, passed ok but still misfires,
so decided to try again myself, before the next CAT goes, (this is the
second replacement).
Hooked injectors and oxy sensor up to oscilloscope set up peg in
throttle to 2250 rpm and took a few observations.
Injector on period dithers about 3ms (under loop control)
No of high counts from oxy sensor = 85 per minute
Voltage from throttle position sensor = varies slightly between .89v -
.9v
After some time at this state the revs drop to approx 1200 rpm,
readings then as follows.

Injector on period dithers about 4ms (under loop control)
Oxy sensor switching, but not counted, it looks normal.
Voltage from throttle position sensor = .893v

Why should injector see 4ms as the correct fuel dose to produce a
switching oxy sensor?
The idle valve has been renewed, (not faulty). But I cant work out
what its position might be set at, or why it should want to be at a
position other than the 2250 rev spot.
Any help would be appreciated.
Tony