I could give you many examples of what is wrong with the NASV bible as compared to God's Holy Word, the King James Bible; but most of what I have learned about the errors in the newer bible versions (especially the NASV) came from an excellent resource book written by Gail A. Riplinger titled 'New Age Bible Versions - An Exhaustive Documentation Exposing the Message, Men and Manuscripts Moving Mankind To the Antichrist's One World Religion'.
Link here to read more about the book and to buy it on Gail's website.
Here is just a little bit from the back of the book about the extensive research Gail did in order to write this book, and also her education and background.
"This book is the result of an exhaustive six year collation of new bible versions, their underlying Greek manuscripts, editions, and editors. It objectively and methodically documents the hidden alliance between new versions and the New Age Movement's One World Religion"
"About the author: G.A. Riplinger has B.A., M.A., and M.F.A. degrees, has done additional post-graduate study at Harvard and Cornell Universities, and was honored with a Doctorate from the College of the nation's largest church. As a university professor, the author taught seventeen different courses, authored six college textbooks and was selected for the Honor Society's teaching award and membership in a national Education Honorary."