I having a query that returns data in 2 seconds (average).
Sometimes, the same query take 150 seconds, for no reason. Executing the
same query, it returns to 2 seconds.
I got this information using profiler.

We're having the general problem that -- in one customer's database --
the performance of the queries varies widely. I've found one example
which is easy to explain and which can be reproduced reliably:
SQL A:   SELECT * FROM table WHERE a = 1234 AND b <> 0

I am having problems when searching my database. I can choose to search in
any combination of: Title, Description or Tags. Searching for any combination
except Description and Tags gives subsecond response times. However, when
searching in Description and Tags (or Title, ...