What`s is the best, or most realiable, or widespread used engine simulation code today?

I`m aware of two options: GT-Power or Ricardo WAVE.

Wich one is best for simulate intake and exhaust interation?

Is Performance Trends Engine Analyzer Pro of any value?

Thanks

Both GT-Power and Ricardo are very good software packages. I'll throw a vote in for Ricardo, because that's what we use with good success.

Engine Analyzer Pro is at best a "rule of thumb" developed engineering tool. It can give you close numbers, but it's not rigorous. It's a "garage buddy" not an engineering tool.