I gave the 400E a heavy duty work out last Friday night. (I think I have heard it called an "Italian tune-up" in these forum pages).
I ran some tests this morning and cannot find any hesitation/lugging on a hard mash from a full stop. And there was just the slightest hint of hesitation on high rpm acceleration....so that appears to be
If this indeed turns out to be the solution I will breath a sigh of relief...
92 400E 128K
99 GMC YUKON 88K