pinto hesitating from 4700rpm upwards

Ok guys, i nearly have my mk1 2 door to a stage that i am happy with. Its on the road and driving at least.
The car has a 2.0 built by the previous owner so i dont know cr or camshaft selection. I had a new set of twin 45 added and a dyno tune completed. I dont put much faith in dynos but apparently it came up at 120rwhp.
It was great for a small while, idles and starts beatifully, still does.
Now when i try and excelerate through the rev range it sort of dies at 4750 upwards.
Previously i was reving to 6.
Prior work was done by a mechanic
Ive spent enough on the car for the time being so i was hoping with a little help i could have a crack at this new issue myself.

Big carbs for an engine only revving to 6?
 
What sort of ignition you got?  Electronic or points?

Blocked/restricted fuel filter.
 
 
 
 

What, explain what is happening above 4750. Does it just not accelerate as hard or starts to run rough. Does it only happen At full throttle

Filter socks often get sucked into the trumpets.
I found this on the dyno with 40mm sidedraught webers - even with springs inside the socks.
Changed to K&N pleated filters. This was with only 95 rwhp too.
 
 
Cheers

Based on the photo of your distributor it looks like it is in completely original condition, and that just may be your problem.
 
You're using points, which over time will wear and the gap will reduce. This result in the points not staying open long enough to discharge sufficient spark at higher RPM, so your engine no longer revs out like it use to. Cheap and easy to test. Use feeler gauges or put a dwell meter on it and adjust you points gap according to specifications. 50+/-2 degrees I think. Once your points dwell is correct, your ignition timing will be out so you'll have to get out your timing light and correct this.
 
If after doing this your car once again revs out like it use to, the next step would be replacing you points with electronic ignition. I have not used the Rob Roy Garage kits myself, but they look like a nice bit of kit. Google it.
 
You will probably also notice while driving that your engine may not go so well and then get up and really boogie around 2000 or so RPM, and you may think this is the cam kicking in, but in fact it will be your distributor advancing, finally providing the correctly timed ignition (to a point) because your ignition advance in your distributor has not been set correctly to accommodate the addition of twin Webbers, most notably the removal of vacuum to the vacuum diaphragm on the distributor. Having your distributor re-graphed correctly will give your engine the low down response that you probably aren't aware of.
 
In short, if setting the points dwell allows your engine to rev out again like it use to, I would strongly suggest getting a correctly re-graphed & rebuilt distributor with electronic ignition and you will never ever have to go down this road again.
 
Good luck.

Revs cleanly throughout the rev range whilst in neutral

it would rev cleanly as there is no load.... 
My 2 cents...  
 
Air... Take the socks off - probably not the problem but for the cost of 4 cable ties, its a quick thing to eliminate
Fuel... Lose that fuel reg (for the moment). I note you still have the side tank - are you aware there is a filter in the base of the tank...Could it be partially blocked. Also how have you plumbed the fuel line in to the tank??? ..I'd recommend you either drop the line at the base of the tank to see how free flowing the tank / pipe is... if the fuel flow seems slow, you could also unbolt the neck from the bottom of the tank to make sure there is no crap there/in the pipe..... If the problem is still there, put a fuel pressure guage somewhere in the fuel line where you can see it whilst your driving,...
Spark. If you can afford it buy a brand new electronic dizzy. If not see if you can borrow one for a couple of hours.
Good luck