thanx vstech I will look it up and let you guys know about my thoughts

-Ive read some of the posts and its really helter skelter on what to do...

take citric acid you buy from ebay
mix citric acid and water (what mix ratio?)
drain radiator and engine block
pour in solution
etch out my brand new radiator and remove rust from the block
run a few minutes with solution and drain. followed by water flush 2x
replace with coolant 50/50 mix?

I understand this helps clean the system, but the car was running cool before. and does etching the entire system promote better interface for heat transfer between the coolant and cylinders? up to 15c? I don't think so.