300tdi flat out at 60?? End of my tether....

Hello all, as title says really, my 300 won't go above 60 for some reason and I'm hoping someone can shed some light.
It's a disco engine, lt77 box, disco 1.2 transfer box with disco axles and she's screaming at 60-65, when I would of thought it should be cruising at that speed. So far I've done the following:

New lift pump (Delphi fitted by previous owner)
Boost gauge plumbed to manifold which reads 1 bar
Pump tweaked a touch
Fully serviced
265/75 greenway macho tyres
Fully rebuilt with pistons rings shells etc

I've searched and searched forums and google for weeks now because I know it's been covered so much but she's running a good 2/3rds throttle and 3/4 bar boost just at 60, and with pedal held to floor it MIGHT hit 70 Sometimes. The confusing part is its not short of poke all the way to maybe 50 ish and flies up long country lane climbs in 3rd with ease, but just looses all will beyond 55. It really is a mission to try and cruise down the bypass ��
Is there anyway of increasing top end/cruising performance so I'm using less pedal and less effort on the old girl? Oh and theres no excessive smoking of any sorts either, just what you'd expect from it. (NON EDC)

have ya got it in low box?

O dear, lets hope not!

is throttle cable adjusted so that full throttle is attained ,clear plastic pipe in between filter and front banjo bolt on injection pump (lets you seee if it sucks air at higher revs while maybe not at lower )small hole in rear injection pump banjo bolt ,timing advanced correctly ,is t/box actually 1.2 ,are diffs 3.54 ?

I've definitely had enough experience with landys to know its not in low box

I set timing with pins etc when I changed the pump to one which I knew was a good one having driven it in a previous disco. Hole in the rear banjo bolt you say? Hmmm shall have to check that one, I have got clear pipe in the line but haven't really monitored it with it running so well lower in the rev range. Will it draw air bubbles when stationary or does it need to under load?
3.54 diffs is a yes and also the 1.2 ratio box hence why it's got me stumped...

Especially as to why it requires so my right pedal to hold a cruising speed.....

sometimes pump needs advancing using progressively small drill bits 9.5 then 9mm on till engine knocks then back till it doesnt ,check cable its adjustable

Right thanks for the suggestions, next thing, can you elaborate on how you go about advancing the pump with drill bits, because that's this afternoons mission when I final work lol.

Just read one of your previous posts on timing advance sorry, so I see where your coming from. Web you advantage pump clockwise, is that clockwise looking from the rad, as in turn the pump a fraction towards the engine?

yes ,clockwise as looking at pump pulley from front,it may not be the answer but cost free stuff is the best to checks correct to start with,

right then, update, Ive bust my thumb open on the 9.5mm drill bit, smashed my little finger against the steering box, but i have had a play with the timing.
followed instruction, and i pegged the pump, lined up the marks on the crank and flywheel, slackened the 3 pump pulley bolts, held it with a bar and 22mm socket whilst i swapped the proper fitting drill bit for a 9mm one. turned the pump against the drill, only to find its fully advanced already. even holding the pump spindle all the way clockwise, i could still get the full sized 9.5mm drill bit all the way in snuggly. any ideas anyone? I'm guessing the last owner fitted the belt without allowing for enough pulley adjustment each way so once I've got more time I'll change the belt and re-align everything as it should be. Then try a couple of degrees advanced.