It could be a vacuum leak, try checking all of the vacuum hoses. It could also be a dirty and sticking EGR valve.
It actually depends on the engine. But if it has HT LEADS (High Tension) Follow these from the distributor or electronic ignition unit and there are the plugs in the manifold of the engine
the spark plugs on a 106 should be in the top of the engine on earlyer models you should see 4 leads conected to them. a later model may not have ignition leads but a sort of ignition pack on top of the engine. the plugs would be under this.
Take off the engine cover and remove the HT leads. You will then see the sparkplugs.
remove the center cover on the engine,two cross head screws this will give you access to the leads and plugs
if you are talking bout spark plugs, they are located in the side of the engine just follow the plug leads from distributer to the other end.
as you look at the engine they are on the right hand side with the heavy leads going to them. there should be four and the leads should come out in roughly a 45 deg angle to the engine
Open the bonnet and you'll see them (With leads attached to them ) on top of the engine block.
replace the ignition leads then try the coil aswell Plugs, wires, cap, rotor, injector, internal engine, etc.
The user manual that came with your vehicle will point you in the right direction. Once you have located your distributor cap you can trace the plugs (either 4,6 or 8) to the side of the engine where a lead goes from each to the dizzy. You then use a spark plug spanner to remove and reinstall your new plugs.
check the rotor botton in the dizzy
could be sucking air through inlet manifold spray wd 40 around inlet manifold with engine running see if engine tone changes if it does chances are manifold gasket needs replacing, also check vacuum pipes for damage hope this helps
4, you can always find this out for any car by having a look under the bonnet and counting the HT leads! *NB - HT leads are the leads from your coil pack which disappear into the engine, which provide power to the spark plugs.