In "default.ide" u can find: 
# Id,	Model name, 	Txd name,	Type 		HandlingId	Game name, 	Anims	Class		Frq	flags   Comprules 
401, 	bravura, 	bravura, 	car, 		BRAVURA, 	BRAVURA, 	null,	poorfamily,	10, 	0,	0,		-1, 0.72, 0.72,		0 
By changing the parameter "frq" frequency i believe u can make those cars apear more times... 
also... 
in "cargrp.dat" u can add "euros" in all lines, just to make sure it will apear in more places, because it will.