Maycom EM-27 Transmit noise

Question

I have a Maycom EM-27 CB radio recenlty fitted into my MINI. When in use I can receive all transmissions from others loud and very clear BUT when transmitting back to them they are reporting that I am coming through very noisy and "crackling". I have installed an in-line supressor on the CB supply but this hasnt got rid of the noise.
Any advice on what to suppress next would be very help full.

Thanks