Good timing of turbo usage is important and getting/saving the cannon for certain stages saves time.
The end of 4th stage was the hardest part for me since you're driving on an overpass and can easily fall off the edge while trying to smash/shoot the target.
Anyone played Knight Rider?....now that game is really difficult. More frustrating than fun and for me, beating that game was a once in a life time occurrence based on pure luck and persistence.