vauxhall 2.0 dti new egr fitted still problems

Hi all, thanks for any help in advance,

I have a 2.0 dti astra van, had egr problem, (no power/ engine in limp mode)
so I bought a brand new egr valve,
old egr was siezed in, so I had to buy a second hand inlet manifold top casing,
took injector pipes off,
fitted used inlet manifold and brand new egr, re-fitted injector pipes,
Van wouldn't start! So got towed by a friend and it started, went for a 50mile drive with no problems,
The next day it wouldn't start again, used a little easy-start and it started and drove no problem,
But then today it started in the morning I drove 50 miles to work with no issues until I came off the motorway and it went back into max 2000rpm etc, so I turned the van off then back on and it was fine again

Please help it's driving me crazy now
ANY IDEA'S PLEASE