I had a toilet clog that ruined the carpet in the bathroom. We removed the carpet and pad and used self sticking tile. Since this was done the toilet won't flush correctly and we noticed that if you take a shower the water in the bowl goes down. The toilet will flush if I have two 64 oz classes of water to add to the bowl as I flush. Can you give me a hint on what to try. I've checked for leeks but don't see any. I have replaced the wax ring and made sure that the toilet has nothing stuck in it.

You still have a clog- in particular it is probably in your vent stack. The purpose of a vent stack is to allow the water in the drain to flow freely. If there were no vent, or if it is clogged, the water flowing down the drain produces a vacuum. This vacuum causes water from other nearby drains to be pulled along with it. If it is in your main stack, there should be a cleanout plug wich will allow you to clean out the remainder of your clog.

That would make me wonder if this house was inspected correctly. The bath room is in a new section of the house and from what I can see it ties into the sewer line in our basement but does not appear to have its own vent. Do I need to add one in or does the vent that the rest of the houses two water spots (old bath room and kitchen) have service. The spot where the new bathroom is shares the wall with the kitchen so could I tie into that one or do I need to run a seperate one. The old part of this house is over 75 years old and the new side is about 7 years old.
Also why did this work before the floor was replaced? It worked fine for about a year and ahalf before we replaced the floor.

Before I answer your query, I would like to ask you one important question. How far away from the toilet is the main stack pipe? This is the large (probably 3") pipe that empties into the sewer and also goes up through the roof.

Its about 21 feet from the new bathroom to the old bathroom and stack.

It is difficult to make determinations without actually being there. My guess would be that there was a partial clog somewhere in the line and after clearing the backup that you experienced it cleared out the whole line causing the problem you now have. A good inspector should have noticed the bathroom addition and looked to make sure that it was adequately vented.
Since it shares the same wall as the kitchen, the installer could have tapped into the kitchen vent, which would be incorrect anyway. There should have been a 3" vent pipe installed for the new bathroom.
One thing you can try that MIGHT help. They sell an automatic vent that you can install on your tub drain (around $5-$10 at any hardware store). You will need to attach it to the top of the drain pipe after the elbow.
Try to extend it up as far as possible. There should be an access cover on the back of the tub and you can bring it up through there if possible. This will adequately vent your tub without causing you alot of teardown and it may be enough to help prevent water from being pulled from your toilet. Any questions or further help you can reach me at drhome@shoppittsburgh.net. I answer those much quicker.

I had a similar problem that came with a house that I bought. I tried a lot of things but when I finally got enough and replaced the toilet, which I couldn"t find any thing wrong with. I set it out the back door for a day or two. The water in it froze and broke the bowl. Then I could easily see that there was a very large comb caught in the curve of the toilet.