Well, the Matrix is the wife's work car for the most part and also our trip car. She drives it 90% of the time and it therefore sits right around the EPA rating. I'm still working on teaching her to drive differently, and its working slowly but surely. Anyway, she makes a lot of trips from company to company throughout the day, many of them are short trips in the city. So, anything I can do to reduce warm-up time should be of benefit not only to fuel economy and emissions, but also to her comfort (yes, bonus points for the husband.) So, I very recently made two grill blocks for it. They've been on the car for almost two weeks now. I haven't pulled her milage book out of the car to see if its helped at all yet. Something to do this weekend.
Before
After. Upper grill block.
After. Upper and lower grill block. I ran out of fasteners so I used the upper ones on the bottom until I ran to get more.
The Paseo is a slightly different story. It was my play car when I was more of a horsepower and handling fiend. It has a cold air intake, header, shaved and ported head and a few other things that of course hurt FE. Anyway, I'm dealing with that the best I can.