well i think your machinist is trying to cover his ass incase he didnt do a good job building the motor. you will only float a valve with old worn out springs, there is no way a fresh set of springs should ever not have enough pressure to do as they please. DSM crank walk is only prevalent in 7bolt 2g motors due to a bad machining of the crank which throws off the thrust bearing alignment...hence why when it happens you can press in your clutch and shove your crank a good half inch into the fender well. been there done that swapped in a 6bolt 1g motor and ran as much boost as I pleased...crank walk has more to do with beefed up pressure plates that it does boost levels....a well built FS series motor should have no problem handling 20-25psi....and yes im aware psi is nothing and I should of stated cfm, but we'll assume its a t3ish size turbo appropriate for the displacement of these motors...with 8:1 compression built motor the last thing on my mind would be something in the motor going...id start thinking about the weak tranny and thin cv shafts that are going to blow at the hp level....