If I remember corectly I did some work with a device that only used the busy
line (a cash till) the printer was conected through this device and the busy
was flaged when the till opned this stops the flow of char's so if the busy is
aranged to pulse after each char then this should hold the PC until it is
released when it can send the next char.

A nother thaught If a small cap and pull up res are used between strobe and
ack this may slow down the data flow sufficently to opperate your device (cant
remember if pull up or down is correct) the strobe pulses are rather short
just streching this pulse may be enough to enable corect opperation allowing
your device to activate the busy on buffer full.

Just a thaught Steve.....