Hello All,

Just moved to AZ here a few months ago and have to get the ol 88 740 through Emissions.... I took it to the Emissions test center and, (out of a possible "2.50 gpm") it got 2.53 gpm ('grams per mile', I believe)...Needless to say, it failed... CO and HC, however, were within acceptable levels... I have noticed that the car has been routinely pinging , especially under load or accelerating from a stop (with the AC on, for example).. despite an attempt to run different, 89&91 Octane fuels.. It doesn't help having daytime temps. in the 100's here either (Phoenix)... I am guessing my engine is (literally) running too hot! Have any of you used "GM Top End Cleaner" (or equivelent) on a 740 or 240, in an attempt to combat carbon deposits?? My engine is a B230F... and has approx 122k miles...
I'm just trying to start at the simple side of things before I consider the Catalytic Convertor being at fault (my suspicion is that the CAT should still be at least *somewhat* serviceable)...
Is there a desired method to apply this top end cleaner (?) - as I believe it comes in a Can (?)....

Thanks to any and all info...

-Miles

'88 740GLE 122k miles