Suzuki: Suzuki Sidekick 96 4wd 1.6, lean mixture, narrow gap

Question
QUESTION: Issues with misfiring?  Problem seemed to improve after changing o2 sensor,
timing belt... But, still a little jitter when I drive around town.  Not feeling the
weakness when I'm on the highway.???

ANSWER: Are the plugs gapped at at least .040?  A narrow gap can cause misfiring at low engine speeds and low load.  I live at about 7k feet, so it became an issue when emissions started causing lean mixture misfire around town in the '80s.
scotty

---------- FOLLOW-UP ----------

QUESTION: I'm not sure about the gap.  Will have to check.  

Recent upgrades...

tune up
alternator
timing belt
O2 sensor

They say it is egr valve. The engine light was on, then off after repairs, now
on again. I don't know exact code, but it indicated egr. Off at every stop,
unless I give it gas. Sticks and jumps, no pick up, terrible gas mileage. There
are many different parts of the egr. Should I change them all?

EGR Vacuum Solenoid
EGR Valve
EGR Valve Gasket


Answer
The EGR valve meters exhaust gas, which is inert as far a combustion is concerned into the intake at partial throttle.  If it's defective, or the system actuating it is defective, you could well get too much exhaust gas, and have a poorly burnable mixture, causing a series of surges, and misfires.  
You could change them all, but it's still difficult to know if the electronic controls are at fault.  Many states have repair legislation that would permit you to request that the repair facility diagnose and estimate the cost of repairing a specified malfunction, thereby eliminating your paying for the guesswork involved in the replacement of multiple devices to find the offending device.   The alternative is to replace them one at a time (might as well flip a coin to determine which one) until the problem goes away.  Not that this is certainly the cause, but sometimes the spring that closes the EGR valve gets weak, permitting a given vacuum signal to open the valve more than the intended amount.  You could try to find a similar year vehicle, and use a vacuum gauge to see if yours has the same vacuum signal in the same circumstances.  Let me know what the final answer is, I'm now very curious.
scotty