Got the new leads and plugs in today, got set of Beru leads and plugs as gambit suggested, half the price of the dealer

What a difference it has made, no flat spot anymore and really smooth acceleration. still burning oil, but only when the engine is hot and has been left idling for a minute or two, I leave it for a week or two to see if the burning goes away, then i'll do a compresion test and see what's what.
Only problem now is that when i take my foot off the accelerator coming down a hill and keep the car in gear (any gear) the car juders back and forth instead of holding steady in the gear.]
and where the injector metal tubes go into the engine (sorry don't know what they are called) there is alot of movement, I can wiggle them on at leats two, could this cause any of my problems?
Any suggestions?