ok, you say the games you burned were originally DVDs, meaning you ripped them yourself? In UK games such as Tekken 4 and Burnout are DVD-Rom (dont know about US).
I have never ripped a game myself, but remember something along the lines of solderless mods (or mods with swaps) cannot boot games over 650 MB data on them. Perhaps somebody could confirm this.
Also, if they are rips then it may be to do with the ripkit that you used.
Burning program wise have you tried using CDRWin or CloneCD if your originals are actually CD-Rom based.
www.psxcopyworld.co.uk for software and tutorials.