http://tasvideos.org/userfiles/download/24370724469822864
So, right now I'm at the first half of angkor wat. Block manipulation is not easy, but I found some interesting things:
1) First way to manipulate block is during the cutscene at the start of the world, based on the frame you skip the cutscene, you get a different set of the first 3 pieces every time
2) During the cutscene after you completed the level, you can press X to get it go faster. Based on how much time you spent during the last leven and how you press X, the first 3 pieces of the next level change. The only problem is that I can't find a real way how this work. Sometimes pressing x for a single frame is enough, sometimes it must be pressed and released some times.
3) During the level, you can manipulate the next pieces by waiting before dropping down the current piece. Again, there isn't an actual precise number of frame you need to wait in order to get a piece change The only thing I've noticed is you can't get 2 equal pieces in a row and sometimes manipulate a precise piece require a lot of frames, and it's actualy faster change tactic on the level.
Last, it will probably be a long TAS for a tetris game, I've thinked to try the expert mode of the arcade game (which if I remember correctly has only 16 levels), but the game isn't in the FBA list, so I can't do nothing
EDIT: Found a big improvement in the third stage of angkor wat, redoing all the stages after this