The LDS-465-1 w/2 hole nozzles(fuel) spec. is 9-10psi at 2400rpm and 4-5psi at 1600rpm(page 34 LDS troubleshooting manual in resources). An engine can be off spec. Put a boost gauge on yours to see how it compares. Can anyone provide the psi specs for the LDT's at 134hp??. My LD-465 got the D turbo [added] and made an est.16 psi (was off the dial at 15) at 2600rpm w/high EGT's under high load. I turned down the IP over 2 turns. Now it's set at 12psi at 2500rpm (or 13psi at 2600rpm which I avoid). It has seen a hard life and has been very reliable. There was a substantial power increase, and smoke reduction. The early style multi-fuel head gaskets had problems. Mine were replaced by bazzokajoe just before it came into my possession.
Engine designers often make housing(s), A/R ratio, nozzle area(turbo), impeller size and shape changes. These can make direct comparisons between a waste gated LDS and a LDS with a LDT D or C turbo difficult. If they did made some internal changes (I do not know but assume they did) the waste gated turbo can make more boost at lower rpm and/or make boost at higher compressor efficiencies (lower air charge temps). The former will make it spool up faster and have a wider power band. The latter will make more peak power , and lower EGT.
The whistle is probably the blade tips, or vortices' coming off them, exceeding the speed of sound.