1990 Jeep Cherokee hard starting issues

Hi, I have a little starting problem and running rough problem, but
the issue is weird, what happens is sometimes my Jeep will not start,
engine turns over, but won't fire up. I fiddled around under the hood
one day and twisted the injectors and the Jeep started! So I figured
it was the O-Ring seals, I replaced them and didn't have any problems
for a week or two, then it started all over again. Sometimes I can go
weeks without having this problem, sometimes I have to twist the
injectors everyday, specially when the Jeep has been sitting for a
while, usually an hour or so...

Also, sometimes my Jeep will run really rough and idle rough for a few
weeks then suddenly I can start it up and it will run smooth, usually
lasts a few weeks, then back to rough again, I cannot afford to have
it hooked to a diagnostic scope, so I am wondering if you may know
what could be causing either of these issues, Map Sensor? Cam Position
Sensor? Crankshaft Pos. Sensor? Etc???

Thanks for any help with this...