From Gurbaani we can find that the actual word is WAHi GuRU instead WAHEGURU.The word WAHi is idication of praise of GuRU.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/sikh-sikhi-sikhism/8193-meaning-of-waheguru.html
This word has great significance in the whole understanding of Gurbaani.As a matter of fact its understanding can reveal a great secret of the whole of Gurbaani.

Another important quote related to this is as
?KEEYAA KHELu BAD MELu TAMAASAA WAHi GuRU TEREE SAB H RACHANAA" pp1403
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=8193

It is important to see that actually here GuRU is being refered as CREATOR not{GOD}

Prakash.S.Bagga