Well this may seem kind of a weird question but does your 7 cause any electrical interference? Just noticed this the other day, my 7 is sitting in the shed and I went to start it up (no exhaust) and around 4000rpm the lights start flickering on and off, not the car lights but the actual flurescent lights in the shed.

 

the sound vibrations are rattling the shed and shed wiring, my guess.

 

possibly if you have something like non-shielded sparkplug wires. it wasn't cold was it?