I'm not totally clear - have you not had a single successful race yet? And as for the radio looping, did you say that it's these symptoms that always occur?
To avoid lag: Make sure you join servers with a low ping - I prefer to connect to servers that show a ping below 100 (particularly if there are a lot of players i.e. more than 16. Thats what seems to work for me).
Your broadband speed, contention and provider will also play a part in this. Search online for a broadband speed test - are you getting what you should be?