I've often thought it'd be fun to build a super sleeper. Something that's sleeper outside and under the hood.
Use about a 92 Laser AWD with no options, real plain looking, hubcaps or some ugly alloys would be better.
Then for power you could do a quiet Supra pump, any injectors, nt regulator, a key diver chip isn't visible at all and would keep the car running right. Sleeper 16g, ported 2g mani, ported o2 housing, there's a few places to hide a MBC or EBC. If you spent the time you could probably hide 2.5" piping inside the factory heatshields and go straight thru the factory cat. IC piping would be hard to hide so ya might have to live with stock... You make it pretty fast though and look totally stock... plus nobody can see what's inside so that opens the door to fancy valve jobs, cams, and pistons.