To make the smoke fade instead of pop, you need to change the last part of the color array. Like this -
Just change the last part of the array to the color and change the last number to 0.
About the jeep, I had to adjust the height that the particles spawn at, which would be +2 more than the normal position. You can change the height of the particles by changing this line in the script - (_objPosZ + 2) - change the 2 to whatever height you want.
About the sparks, yeah... That kinda slipped. The problem is that I cannot include the sparks in the main script, as the script loops way to fast for a few embers to be ejected into the air. So I had to make some kind of an estimate... Turns out my estimate was quite wrong.