Newbie Asking for help on 1g gs

[fluxhomemade]

I own a 90 gs and it would (still does) jump around under 1000rpm it is insane i thought it might be a vacume leak so i looked around and on my Evap emiss canister the middle plug was missing so i replugged it and it started to idle at 1500rpm i quickly adjusted it to get it down to 750 - 900 it was fine for bout 3 weeks then one day it started to smoke not too bad only when i was in drive with the brakes on but not in park (no check engine light or overheating it ran normal ... course my front pipe is all messed up and leaks so it might be just that) now it still ideals insane from 500 to 1000 back n forth it will some times smoke its only smoked 2 times im getting my front pipe in a day or two but ive noticed oil on my head shield looks like a blown head but no power loss and im confussed as what might really be wrong

 

[fluxhomemade]

I own a 90 gs and it would (still does) jump around under 1000rpm it is insane i thought it might be a vacume leak so i looked around and on my Evap emiss canister the middle plug was missing so i replugged it and it started to idle at 1500rpm i quickly adjusted it to get it down to 750 - 900 it was fine for bout 3 weeks then one day it started to smoke not too bad only when i was in drive with the brakes on but not in park (no check engine light or overheating it ran normal ... course my front pipe is all messed up and leaks so it might be just that) now it still ideals insane from 500 to 1000 back n forth it will some times smoke its only smoked 2 times im getting my front pipe in a day or two but ive noticed oil on my head shield looks like a blown head but no power loss and im confussed as what might really be wrong

and the smoke only came from the back near under the intake mani.