I tried again - 7th try yielded new highscore! 
Looks like it´s InfuriatedBrute's turn to beat that ;D I guess I´m first to reach level 21. I did the Maths... in theory you can get up to around 1400 points by getting up to level 138 and only having permanent speed upgrades spawn. Then in last level only $s. This way you will be first position all the time, you will be at times around 10 times faster than the computer enemies (in level 5-10). But there´s a downside: likeliness of only permanent speed boosts to spawn is low... that low actually that winning the lottery twice per round would be an equivalent... for 138 rounds. In case you beat that I bet you should start playing the lottery instead!
So as for strategy: Always get permanent spped upgrades. Use Nitros in earlier level to gain access to a permanent speed boost and still finish first. restart first level until you have at least 190% permanent speed after first level. This way you have plenty of room in the next 5 levels to get all the upgrades and still easily finish first. On this try I had been 3 times as fast as the enemies on end of level 3. That being said - I´m eager to see who is obsessed enough to get above 500 points or to level 25 first ;D