I think this best describes the circular progress of this game in general. It takes hours to gain seconds of driving, and then I have to go back and try it in a different way, or optimize it more. (I'm actually thinking test runs of each stage aka 120 Star would be beneficial, I'll look into that.)
There's a theoretical shortcut, which 1) hasn't been done yet, and 2) I mentally calculated to be slightly slower. So no shortcut for this stage. In the end, too many courses all with the same boost off CPU trick will get boring, and don't you want to see some killer expert driving as well?
MMF is tricky; it's very bouncy. you get too much speed, and you'll be in the air and then tossed like a rag doll. sometimes you'll want to go down a steep hill, but you're going too fast, and you're in the air; you go faster on downhills. Knowing which hills to go up and which to go down takes a lot of testing. I have to constantly watch my speed (I am actually very in favor of the end .m64 having the beginning C-right input being taken out so that the entire run is shown with the mini map.) The moles are luck manipulatable, which also means that at random times I'll have shroomed around a fence and WHAM! get suddenly hit by one.
Lessee, tack on some mushroom manipulating troubles every now and then, throw on a sprinkle of family reasons that can make me not work on this (early bed time, "get off computer!", etc. I swear, I can get more done at college), and have a final topping of Fried-making-sure-I-redo-segments-to-gain tiny-amounts-of-frames? That right there is the Mario Kart 64 150cc GP TAS Sundae Ice Cream in a nutshell!