>>To date, my experience with SQL Server,
>>tells me that if the relationship SIZERAM / SIZEDB is very small 1
>>it is common to have performance degradation.
>>Certainly the size of RAM it must be larger than the size of the Client table including the indexes.
>
>The size of that table is 40 GB.
>
>I have requested more RAM since a very long time.
>
>>Another issues it is a bad optimization of @variables.
>
>Are you saying that protection for SQL injection should be removed from all the commands? Parameterized approach has always been the case since a very long time. Or, is it that you are suggesting to avoid the SQL injection approach ONLY when using the full text index and use a direct approach instead?
>
>IAC, I checked the execution plan on the direct approach and I have attached the file.
>
>SQL Server seems to have offloaded the request to current index and only needs 1% from the full text index.
>
>How can we explain that?

I do not trust a lot of numbers that shows the sql plan.
How many rows back?

try

SELECT Client.PrimaryKey
 FROM Client (NOLOCK)
 WHERE Contains (Client.VehicleModel, @VehicleModel)