Hi gave buddy my 89bonnsse 8 months ago it passed emission test,this week it failed horribly,what can he do to improve emisions other than plugs and wires.
Also cleaned intake up to butterfly valve,how do you clean past there ,can I unbolt it and take it off and clean with carb cleaner.thanks

Check out the EGR valve, and have someone check out the catalytic converter. You could prolly do it yourself, by hitting it. If it rattles, its done. Also ask the shop to take a cat back pressure test.

Replace the oxygen sensor, air filter, and you should be good to go, along with the stuff you mentioned. These engines burn very nicly, so its rare for much to go wrong there, like the cat.

thanks what about taking off throttle body ,is there a gasket or does it just unbolt ,clean it ,and bolt back on.