The fuel rail pressure regulator hose goes directly to the short nipple below the idle stepper motor bypass hose nipple on the back of the plenium, hard to find but important and MUST BE AIR TIGHT FOR THE PROPER VACUUM SIGNAL TO THE FUEL REGULATOR. A must check as the fuel rail pressure will be screwed up. When the regulator screws up you'll know big time. BTW those Lucas injectors suck, Bosch disc 4 hole vs single squirt atomize way better called a newer design after these Lucas injectors. This off late 351 Ford engines after flushing and flow balance checking to within 0.4% a set of 8. This took 42 to find a balanced flow set with a PWM and adjustable Hz controller with ultrasonic cleaning first at my home shop. The dizzy nipple on the far side away from the dizzy connects directly to the nipple on top of the plenium chamber top. The nipple near the dizzy just add a cap to keep dirt and crap out. I would bet you a 95% chance the vacuum advance unit is also shot and leaking and your not knowing it. Give the hose the suction check with your tongue as a stopper and see if it holds a vacuum. I'll take my stout bier now thank you please. That nipple on top of the plenium is not a huge vacuum leak as posted above,it's ahead of the throttle plate with no vacuum applied at idle (wow replies) it steps down to a pin hole of only 0.021" just ahead of the throttle butterfly. At idle until the butterfly moves app 1/8" before any vacuum signal begins to pull on the vacuum advance unit. With that small 0.021" restriction hole for a slow vacuum advance response it doesn't take much of a vacuum advance unit failure for this signal to be lost. The Stealers want $155 for that POS item that lasts from 13-17 months on average at best and slowly start leaking and fail without you knowing it. I went thru 3 of them before waking up. Better units rebuilt with better materials inside come from Oz. My last one lasted 7 years besides have 4 degrees more advance than the California spec crap units. I installed another one from Oz last week. First one was $75 USD shipping included, $125 today. I also opened up the vacuum signal at the plenium by 2 1/2 times more cross sectional area this quickened up the advance and throttle response. Other machined trick intake items just added with also great results. I also bet with your many miles the throttle plate isn't at 90 degrees from the intake inlets machined surface measurement point but over center so your closing throttle before going open again, it should be within 0.019" across the butterfly face. When was the last time the centrifugal advance was cleaned and greased? Minor items owning a dizzy motor but far cheaper and adjustable than coil pack failure replacements plus you can change the advance curve and timing. This is what woke up my 5 speed besides repositioning the TPS to the RPI chip. I'm a 4.6 litre with a dizzy. The other nipple off the left side of the ram tube base goes to a "T" that connects below the TPS and the oil vapor seperator on the right front valve cover. Don't forget to connect the hose from the rear of the left valve cover to the top air filter cover nipple pointed at the left fender. On the right ram tube base the rear nipple with a vacuum check valve to the brake booster, forward or center nipple to the carbon canister near right fender, front plugged off a vacuum test port. This on 95 with the older OB1 3.9 motors accessories on a 4.6 shortblock. I forgot you may of replaced the Rover ignition wires, good choice, I run (RIP) Crane Cams 50 ohm per/ft Fire Wires that alone gave me more spark energy at the plugs.
Now I just bump the starter hot or stone cold not even hearing one cylinder over compression it lights off instantly.
In the IAC bypass hose I added a mini revolver cylinder looking plug with a washer with five 1/8" holes with a center locking screw to make a adjustable restriction for the cold start fast idle limit of 875 rpms, less cold engine wear plus a preoiler I added to the new motor. I start cold or after a overnight oil drain with a dry 7" long filter with a pressurized motor of 26 psi oil pressure before starting. Port match the intake and cast iron exhaust, Borla exhaust with high flow cats it will wake up plus gain in mpg. Oh a brass slug with a 1/16" hole to the plate below the throttle plate plenium for a cooler intake air charge. I run a cold ram air intake also. Nuff rambling off hope this gets you started. Cheers.