[V8] My '90 Pearl is dying on me!

[Peter A. Green]

My Pearl has started dying on me...  it starts fine but loses power after 50 or a 100 yards.  If I apply pedal she regains engine revs and is happy for about half mile after which she again loses power and I again go through the procedure of applying pedal.  It reminds me of when I got water contaminated gas (in a previous car) which clogged the gas-filter.  The situation has quickly deteriorated and is now at a stage where I can't take her out in traffic.
Has anyone 'been there had that' or have any idea what is wrong with the dear old girl?

Pete