put it this way....A Ls redlines at 6,800-7000rpms..A GSR or Si red lines at 8,200-or 9,000 rpms with chip....Now without building that LS up it wont be able to handle the high rev for that long,before it starts breaking shit ....Cause that Ls has never in its life seen 8,200rpms and taking it there is dangerous with out building the block up, And getting all the oil inlets switched to ones off a Si or GSR so that it will be oiled properly..If not the stock ls ones won't inject enough oil and it will start to burn up the block and pistons....
Im just going on what it said off the import performance page...
It also says there possible to build but need to be built the right (all work done by a machine shop) to get them to run and last for ever like stock honda engines are known for..