Hey Bigg... if you already noticed some gain on your low-end... even before using the purp... don't bother putting it in... Let me borrow it... I want to put it on my mantle too. I need some low-end improvement too... ;oP haha... anyway, let us know how things go when you do get it in there.
As for changing the ATF in the converter...
-some other forums talk about disconnecting the ATF cooler lines (from the radiator... or from external cooler), and start the engine to pump out the old ATF into a jug. as soon as it bubbles... then shut if off, and refill it manually through the other hose. Do this about 2-3 times and they say the fluid will be clean and bright. About 14-15 qts used.
-Another way to change ATF easily at home, is to just drain, change filter, and refill... then after 100 miles... or up to your next oil change, drain the fluid again (you added the drain plug on your ATF pan the first time...right?) and refill. Then do this one more time (3 time total) and they say your fluid will be very clean and bright. This should get the fluid in your coverter clean. (I did this on my '03 Accord at 50k miles... this method worked well, and easy. I actually noticed real improvement from the first initial drain/fill... the second time, I didnt feel any difference, but the fluid was very clean. I never drain filled the 3rd time)
-From what I've seen, some cars have drain plugs on the converters, and some have a window you can access to get to this converter drain plug... otherwise you have to remove the converter to access it. A nice shop manual may be able to enlighten you on this one.
Good luck!~