Could someone tell me what factors affects to the size of WG ? What size of wastegate would be good for my setup? Does it make any differents if I have 25mm wg or 45mm if I´m running only 14psi boost pressure level ?

 

with a 60-1 and a 1.15 ar you should be able to get away with running a pretty small wastegate... however 25 mm sounds a bit too small IMO but somone else might know better than me for your setup.

and the less boost you want to run the bigger wastegate your gonna need

 

buy one and only one. thats what i did..........HKS racing 50mm. that way if you ever want to get a bigger turbo, one less thing you have to worry about later

 

How about two smaller sized wastegates, one on each manifold runner?
Cost should be about the same (maybe a little more) than one monster sized one, and response and flow should be even better.
However, more plumbing, harder to install, design proper manifold, etc is probably enough to add up costs and headaches to make it unfeasable.

 

what did you just talk yourself out of that one...
About the original question I also recommend getting something large that way you don't have to worry about it. Say you get on that is too small, then you get creep, have to take it out and sell it and waste more money, then buy the bigger one you should have started with