Spark Plugs

[CanadianZ71]

I just changed my spark plugs - they where badly worn - with a new set of Bosch +4s.  The improvement in power is noticable.  The truck now rips rubber pretty well from a stand still and I am happier with its starting.  One thing, however, bothers me, the truck now has a noticable engine shudder while idling.  The RMPs remain constant but the truck shakes slighly while sitting.  Anyone have any ideas?  The plugs I took out where ACs and I'm not sure how long they where in there as they where worn pretty well and had some 'rust looking' deposits on them.  I havn't put many miles (maybe 10) on the new plugs so maybe the engine has to adjust?  Thanks for any feedback.

[SilveradoWV]

Our 91 350 shakes or studders all of the time when its ideling??? It has done it as long as I can remember, so if you find out the problem, let me know!!!!

[CMNTMXR81]

See my response in this thread;

 

http://www.gm-trucks.com/cgi-bin....t=11083