Toto Drake Issues

I've now had my 2 Toto Drake's for about a month, and I have the following questions and observations:

1. Flushing is always complete and reliable
2. One of the toilets dripped into the sewer line for 10 minutes or so after flushing and whenever an addition was made to the bowl. This was corrected by calling Toto and having them send a flow restrictor for the line leading to the overflow tube.
3. The tank on one of the toilets is angled forward a bit. Does this mean I overtightened it?
4. Compared to my old 3.5 gal American Standard toilets, the Drake's flush more reliably, but the bowl gets dirty more easily. Partly this seems to be due to the fact that less of the bowl surface is under water, but also the surface under the water seems to remain dirty more often, sometimes requiring a second flush and defeating the purpose of a low flush toilet. Has anyone else had this problem? Any ideas? Are there products that can be applied to the porcelain to make it more difficult for the fecal matter to adhere to the surface?

Water depth on toilets is determined by the top of the trapway bend.

The water will continue to fill until the tank is full, which may mean that some water will fall over the "dam" of the trapway bend in the bowl.

This is how most brands of toilets work.

The newer 1.6 gallon toilets do require more cleaning than bowls with more water going through them.
Even washing the car, the longer you put the hose on the spot, them more dirt comes off.