Resistor to tone down tweeter?

Certainly treat the first reflection points in your room. Also if there is a wall close to your back. You can get some panels from GIK http://www.gikacoustics.com. I prefer them because they work well, are very reasonably priced, and for WAF you can get them covered with acoustically appropriate material of any picture/photo you wish.

Also recommend less toe-in so tweeters are not hitting your ears so directly.

And if your baffles have relatively sharp edges or are wider than your drivers, try a pair of natural wool felt pads from Jim at http://www.diffractionbegone.com. These reduce HF baffle reflections and corner diffractions.

And for a quick and cheap bandaid treatment, tape a small piece of paper towel so it hangs over them. For WAF use the kind printed with pretty stencil :^).

If the tweeters are different, make 'em match.
I'd personally only replace tweeters in pairs.

Was the new tweeter supposed to be 'just like' the one removed?

Magfan
Yes it was. The whole tweeter housing has to be changed on the Focal 918 because they are so custom mounted. Wish they would have spent more on the tweeter than the custom mount.:)
They are the same model # also.
Im quite happy with the difference the new tweeter made. I dont notice a huge difference but I think because the old one was in such bad shape I was used to hearing that sharp metallic sound from my right speaker...now the brightness has shifted more to the left. (much less than before though).
BUT my room has two windows with wood blinds on the left side and not much as far as covering the walls. The right side has wrap around sectional-couch and is open to another area. (no corner/wall)
With that being said I would think the left side would produce more echo/brightness right?
Im thinking I should focus on the back wall/reflection point and the left corner/windows.??

I would think before you go invest in Soft material like curtains and or Carpets etc...you need to get both tweeters running the same..My first action would be to make sure both tweeters exactly the same then deal with room next.....

First of all, make sure the tweeter is OK. Both channels should sound the same. A damaged voice coil, or something else in the tweeter can cause this.

If you find both tweeters to sound the same, maybe your sensitive to their resonance (usually right over 20 kHz) like a lot of people are, or just the speakers design.

You can try adding a non-inductive 1-4 ohm wire wound resistor in series between the plus wire and the tweeters input plus (+) terminal. The larger the ohm number you use, will result in less output from the tweeter. Maybe try a 2 ohm to start. This will tame the tweeter down. You may, or may not like the results. I have done this myself with good results. Here is a link to give you an idea about the resistor. Link.[http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=345]