Hi guys, I have recently purchased a 89 311 SR1 with thunder exhaust and silent choice. Any ways, my air pump for the silent choice is pooched. Its a Thomas pneumatic pump model 315CDC40/12-175C The manufacture told me they were also installed in the automotive industry too but stopped short of telling me what specific models and years.I can buy the new updated pump but I wanted to try and find a good used one. Anybody have any idea.

your the first I'm hearing of an SR1 with silent choice

Was gonna say the same.

My 89 292 SR1 has silent choice as well.

your the 2nd....

Hi guys, I have an 89 311 with silent choice and Thunder exhaust.

I know you have a specific question but Stock silent thunder isn't very loud. It's not much louder than through prop.