change thread priority of dragon age inquisition

I'm trying to get this game to run better on my dual core processor, I used a program called Process Explorer to see that the game runs with 15 threads, 4 of which take up around ~98% of the processing power at one time. I found one thread that uses 10%-30% of the cpu cycles which does not impact gameplay at all, suspending this thread gave a dramatic boost to the game performance. I'm thinking if I can adjust the priority of the other 3 main threads, I can further improve the performance.

So the question is how can I write a program that changes the game's thread priority given thread ID's as inputs?

In C++ there is a function called SetThreadPriority() but this requires a thread handle, but this seems to be used for threads of the current program only.

I've been reading about dll injection, previously this game couldn't launch at all on dual core processors, and the solution was to inject "dualcore.dll" using a program called Extreme Injector, is there a way to see the code of this dll and how can I write my own to modify thread priorities?