I think there are a couple of reasons:
1. COST is pretty huge
2. Only so-many kits available
3. Generate alot of heat
4. Require more up-keep than a supercharger
5. If it isn't tuned right it will hit MADD boost levels thus, killing the engine
6. Lag, exhaust driven and requires time for the exhaust to flow at a quick enough rate to produce any power.
7. Just PLAIN psycho!!
8. I'd love to have one!
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C ME FLY
88 coupe
14.75 @ 98 mph
Traction Limited