Tony, in my opinion, no. If anything, the oncoming air at near 200 MPH might even be blocking the exiting exhaust. Leaving them in a trailing angle and not cut off, may well add a scavenging effect.

Best,
 
I asked Larry Vetterman about this and he said to NOT cut the tailpipes. Larry mentioned that a few people have and end up calling him for replacements when they realized that it reduced engine output.
 
Exhaust pipe exit.

I asked Larry Vetterman about this and he said to NOT cut the tailpipes. Larry mentioned that a few people have and end up calling him for replacements when they realized that it reduced engine output.

Thanks... I won't touch them.