Wow that's pretty amazing attempt. Looking at your gaslog that's pretty amazing too.
It looks to me that some of your biggest improvements came from heating the intake air and from using sommeander's grooves? Or do you think it just coincided with improved driving? How are you going about heating your intake air and how much are you heating it?
Don't overlooks the tires at 60 psi, belly pan, and grill block. This heated intake air concept needs the grill blocked to be very effective.
I think the Somender Singh grooves are a factor. They would be more effective if I could find flat top pistons and get the compression a bit over 10:1. I am working on that but I am not going to pay $500 for a set of custom pistons.
Saturns respond very well to heated intake air. Most say 180 F is about right. I now own a 99 and an 01. The programming is different on these two cars. My 01 runs fine to 200 F. There is a little missing just under 3000 RPM. There is a large power loss but the mileage is good. There are several things you need to do to get the hot air. Here is how I did it.
1. Relocate the IAT sensor from the horn into the main body of the air cleaner. This will require a 1/8 inch pipe tap. I put mine in the in the lower front middle.
2. Plug the cold air inlet with something. I used a soft toy ball squished into the air horn.
3. Remove the plenum and find some tubing that will fit the plenum hole, about 1.5 inch OD. Run some heated intake hose, you can buy this at auto parts stores, from the air cleaner over to the exhaust manifold. Others have used dryer vent hose or similar.
4. Form a thin sheet metal house over the exhaust manifold and tuck the hose under it. Mine is very crude. This could be improved a bit. Actually if one needs to increase heat transfer from the exhaust to the air a system sometimes used on experimental aircraft is to take a long small diameter spring about 5/16 inch in diameter. Over-stretch it so the coils are separated 1/8 inch or so and wrap it around the exhaust. I have not done this but it is a possibility.
With outside temps below freezing this is not working too well even with the grill virtually totally blocked. There are a number of areas where air leaks in. I bought a small heater core to use water to preheat the air but I have not built anything to use that yet. That would go into the bypass circuit.
Too many ideas and not enough motivation to do them. Some have benefit just by tricking the intake air temp input with a resistor or combining it with heated air. Fake heat made a dramatic difference to my scangauge numbers but the fillup at the station was disappointing.