It's pronounced TAKH-voh. In Finnish, the "h" is pronounced similar to "ch" in Scottish "loch" when it is followed by another consonant. So leaving it out would change the sound quite a lot.
Tahvo's a pretty cool name, in my opinion. If I were going to use it, I'd rather spell it without the H, as Tavo. It looks better in print that way to me.
https://fi.wikipedia.org/wiki/Tahvo