1:49:21 (2m 19s) might be able to go lower if you get the perfect start.

If you get a similar RNG to what I got:

Oil Fields:

Pre-fire two rockets then whammy spammy Beezwax this will get you 12 seconds.

Ski Resort:

Use the special on Sid Burn then go and pick up the bulls eye rockets and then whammy spammy Loki.

Ghost Town:

You need the special on the edge at the beginning. Get the special and immediately switch targets to Boogie and use it, it seems to hit him 100% of the time. Then go up the hill and drive to the brown crate (on the rails) which will give you another special, use it on Molo then after that go to the train and finish off Beezwax but becareful of his special.

Aircraft Graveyard:

Save the double damage for Houston.