Testing (sarge) is currently at 3.3.4. If you really (really really) need 3.3.1 speciifically, try finding an archived .deb package of it. I haven't had to do this myself in years, but building gcc can be convoluted, and you may discover you also need specific versions of binutils, glibc, linstdc++, gmake... There are sites archiving all historical versions of past debian packages, but I can't seem to find a quick link; sorry.