Replicant, right for your chest this is best. Instead of doing bar presses, use dumbells, Use the same weight for at least 6 months. This means both sides of ur body have to heave their own weight and cannot help each other, it also means that eventually even tho ur left side will find it easier ur right side will find it harder until it eventually catches up to the level of ur left side.
And for arms, thats easy too, dont work ur left arm! doing bicep curls etc just use ur right until it reaches the size of ur left. Its the only way :] its common sense really!
If you wish to still use the bar DONT, but if ur insistant, you can hold the bar in a way were ur left arm holds the bar normally, and right does a wider grip that will work the right side of the chest more. Obviously if u do this ur gonna have to lower the weight a little. But i reccommend the DB tip I gave at 1st.