I need to search words in title and tags only, how to do this?Thanks

I already replied to a similar inquiry so I will just quote myself -

The K2 plugin relies heavily on the core K2 code to do the heavy lifting. This is very efficient for writing modules, but it means that there currently is no way to filter the search by category. You would have to hack the core to use the current module. The better way would be to write a whole new module with all the code self contained in order to allow for category filtering.

Same thing applies here. You would have to code a module specifically to do this since there is noway to do it currently.