20k is a good time to flush. in all honesty the only way to keep these s/c cool is to replace the h/e with a larger unit, ie: needswings or tigheds supercooler. adding a larger flowing i/c pump and separteing the coolant system and i/c system along with a 180 tstat and -10 fan mod will ensure the car runs cool and stays strong. the total for all these mods is approx. $650 and you will see the benefits for yrs to come. its some of the best and most inexpensive mods you can make