You will need to tweak things a little bit - not much. You are effectivley upping the compression ratio when you remove the break in shim, so this will effect the tune a little. An 1/8 to a 1/4 of a turn should do the job. You will most likely need to lean things a little. Just follow the tuning guide and retune the LSN first for a smooth take off and good idle, then tweak the HSN if needed for a good clean top end. If you needed up to a 1/4 turn in the HSN to get things right on the top end, then revisit the LSN and check that again too. The HSN needle has a direct effect on the LSN - ie when you lean or richen the HSN to any significant amount, you effectively lean or richen the LSN at the same time (as the HSN regulates the amount of fuel the LSN receives overall). So the order of events for a full tune would be - check and set idle gap / adjust LSN / adjust HSN / recheck LSN and tweak if needed / set final idle speed if required (be aware that adjusting the idle will also change the LSN setting, as the LSN needle is fixed to the spray bar, so you have to balance any changes here out as well . No one said it was that simple
With the newer GX Series motors you will probably be able to take the break in shim out earlier, say 20 tanks, as these new motors are not as tight as the previous models. You can break them in without the extra shim fitted, but it does alleviate some stress and strain on the internals during the first 10 or so tanks by dropping the compression using this shim. It is recommended.