Being under the limit is just one way to prove intoxicated. You can also be intoxicated because you lost your mental or physical faculties as a result of the introduction of alcohol into your body. Some people can reach this point of impairment even well below the per se limit of .08. But even more apparant is the fact that alcohol is just way to intoxicate yourself. You can smoke crack all day long and you'll still blow a 0.00, or you could ingest some prescription drug and just drink a few beers and reach .74 and even though that alcohol alone isn't enough for you to be intoxicated, the combination is.
People always complain that they are damned if they do and damned if they don't when it comes to the breath test. Even if they blow a 0.00 they are still going to be arrested, and if they blow over the limit it will just be used against them, and its true. But the reason is because the officer really can't just ask you to go take a breath test (actual intoxilyer, not the PBT). They must determine that there is probable cause based on perceived impairment, or do some sort of other preliminary test like the PBT. So even if you later blow under the limit, it doesn't change the fact that the officer already had probable cause for arrest.
In terms of license suspension, you are alright...for now. If you refuse the test you are suspended, but if you submit and blow over the limit you are suspended as well. Since you did take the test and came under the per se limit, than you will not receive any license suspension as a result of the breath test administration. If you are ultimately convicted of DWI however, than your license can be suspended for that conviction.
