Lately the pedal has been mushy, and when I'm sitting at a light I can push the pedal down to the floor.
I thought it might have been air in the lines, and its been a while since I bled the system and now the problem seems to be worse.

Everyone I've talked to seems to think its the master cylinder.
Is this something I can replace myself? I'm so-so on working on cars, but I can change brake lines/calipers myself. Is this much more difficult than those?
Does anyone have a good how to or write up?
Should I get an RS cylinder, or can I upgrade to GSR? If I upgrade to GSR do I need new booster too?

Thanks

 

up

 

Why dont you try and flush the fluid first.

 

you should bleed the lines again and if the problem persists take it to a mechanic to have it bleeded.

 

Edit..
i have flushed the system.
That is what seems to have agrivated the problem.
Sorry I didn't make that clear.