Tucker
The fuel system basically consists a pump at one end, in the tank, that sends fuel up a long pipe to the engine bay, through the filter, then round a circuit of pipes to the injectors at the other end. For it to work properly though the fuel in the pipes has to be maintained at a continuous pressure, so that when the injectors are activated by the signals from the ECU there's enough fuel actually in the feed pipes to squirt into the cylinder head and power the pistons. If the pump isn't strong enough, or something is allowing fuel to escape out of the feed pipes prematurely, that will cause a drop in fuel pressure, which in turn will cause poor or unreliable engine firing. In your case the continuous smell of fuel is probably giving enough of an extra clue that the problem is more likely fuel escaping, so that's probably where to start looking first. Assuming you've changed the fuel filter recently, the next thing to do would be to check:
- condition and fitting of your fuel lines. All rubber can get slightly porous with age, so it might be just as simple to replace them regardless. If you're doing that, you might as well go with braided if you can afford it.
- fuel rails. Not often heard of them failing, but you can't rule out that one of them has a very small hairline crack, or just isn't fitted properly.
- injectors seals. More rubber, in the form of o-rings. If you're going to pull these out, the best option is to have a reconditionned spare set ready to go straight back in, with new o-rings. Plenty of places do them on an exchange basis, the main points to look out for are that the set they'll give you is flow-matched, ultrasonic-cleaned, and comes with new o-rings. Figure on around £15-£20 per injector, plus a little for post, but check locally if there isn't a specialist near you who does them for less.
- fpr (pressure regulator). Again, not often heard of them failing, but any original part on a classic is going to be at least 10 years old, so you can't rule it out. You could try to pick up a low-mileage one that someone's sold off when they upgraded, to save cash - usually a fair few around either on here or Ebay.
Walbro is never a bad idea, especially if you've already got any power-mods on your car.
Parallel fuel-line mod has plenty of how-tos and guides on here and other sites, but isn't a good idea if you're not confident you'll do it exactly right. Pi$$ing fuel and hot engine parts are a very, very bad and potentially dangerous/expensive combination.
Neither the walbro or parallel mod would need a remap or new ECU.
Heatshield on Turbo not a bad idea either, generally, but I honestly don't think it's directly causing your problem, from everything you've said.
cheers
Mark