If you eat bread made with malted barley flour-will it show up on EtG test?

Don't know. There is no research involving that particular commodity.

Closely related however it has been demonstrated that bakers yeast and sugar will create EtG via intestinal fermentation.

Ref:
Thierauf, etal, 2010 (http://www.ncbi.nlm.nih.gov/pubmed/20655676)

NOTICE: Any person or entity that is subjected to or relies on EtG testing should read this Advisory issued by the US Department of Health and Human Services, September 2006 and remains in effect as of date of this posting. Copy available here > US DHHS Advisory (http://kap.samhsa.gov/products/manuals/advisory/pdfs/0609_biomarkers.pdf)