before a purge, try an Italian tune up.
basically, get the car on the highway, and drop it into 2nd gear as you accelerate up the ramp TONS of smoke will billow out the tail pipe. hold it near 4K for about 30 seconds, then drop it up to 3rd and accelerate up as fast as you can and then let it shift up to D and drive normally.
do this twice then see how it runs.
it's best to do this after the car reaches full operating temp though.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!