Dear David,
This seems more reserved than what you note, but this is from his introduction: "If lines 189-220 of 'The Vanity of Human Wishes' are not poetry," T. S. Eliot commented, "I do not know what is."
However, Eliot discusses Johnson at length in On Poetry and Poets, the chapter on Johnson's criticism and poetry.  Also, I don't have that edition of Johnson, but I found the quotation on Google listings of it.  You might find more quotations if you run through the list because it seems to TSE seems to be quoted as praise for the book.

>>> David Boyd <[log in to unmask]>09/04/10 12:37 PM >>>
OK, Mike, sorry can't help further.

On 4 September 2010 16:23, mikemail <[log in to unmask]> wrote:
Thanks David, I had this page it's the specific lines which Eliot actually mentioned I am trying to find. I made a scribbled note but have recently returned to Saudi and I thought it was among my luggage..I live in hope, still searching.
----- Original Message -----
From: [log in to unmask] href="mailto:[log in to unmask]" target=_blank>David Boyd
To: [log in to unmask] href="mailto:[log in to unmask]" target=_blank>[log in to unmask]
Sent: Saturday, September 04, 2010 5:31 PM
Subject: Re: Eliot's opinion

Might it be

(various online texts of the poem are around, too.)
On 4 September 2010 14:10, mikemail <[log in to unmask]> wrote:
I recently came across a copy of A Poem and a Vanity of Human Wishes by Johnson.  The introductory essay by TS Eliot 1930.  Can someone direct me to the lines which Eliot considered an example of good poetry -the best ever written - I have lost the reference which I took from the book.