Like most things, you get what you pay for. Do you really expect a $225 insert to work the same as a $1000+ true LSD? Sure the insert will probably help but it won't perform like the real thing. I would think just installing an insert would still leave the stock diff prone to explode with wheel hop? (real LSD like the Quife should prevent this).

My thoughts are, if you plan to make 500+whp, why are you looking at such a cheap solution for the item that puts the power down?

My car was fwd, I ran a Quaife. Last time I had it dyno'd in street trim it made 410whp/352ft/lbs. Having first hand experience with a 400whp+ fwd, my advise would be skip the LSD & swap to awd. The car is so much better in awd form & from experience I would never build a high hp fwd again.