IRS Transcripts ONLY are Good Enough!
Firstly you may not be asked at all for the IRS tax returns..
Secondly, if you owe IRS somethings, they would know it[FBI/IRS checks during I-140 I assume]... then they will ask for your transcripts/W-2s etc... Thats it! FOrget about getting scrutinized! You are not dealing with IRS!
Relax - if you do not own a dime! Just go and you will be fine!