A 347 that we installed at work had a pair of Hooker short tube headers on it that had many leaks where the pipes were welded together at the collector. We needed to remove them and weld them up.
First- take-the-time an' effort to actually figure out what's wrong.
Second- the answer may be obvious but won't hurt to post it just
to get some feedback on what others have done to fix theirs.
Third- decide what to do and do it.