The 240Z engine is a remarkably simple and well-built device... except for the emissions control system. The latter is a train-wreck, typical of the auto industry's late-1960's, analogue-era, pre-ECU/fuel injection, band-aid solutions. The problem was not unique to Nissan. Whether it was the USA, the UK, Italy, France, Japan -- they were universally bad. Why? Because the technology available to the industry that was 'ready for prime time' (i.e. wouldn't get the manufacturer sued for incompetence) was nothing better than a lash-up. In the end, the only answer proved to be a combination of electronic fuel injection + computer control. It took almost 10 years to get there. In Panama, you are re-living the 1970 Los Angeles nightmare -- high temperatures + traffic jams + complicated, ineffective smog equipment technology. Plus -- as I mentioned in an earlier post -- the pssibility that your local gas may be substandard. My advice: 1) Remove all of the emission control equipment; 2) Run the tank dry and then fill up at the biggest, brand-name gas station in downtown; 3) Place your trust in a top-quality auto shop that has a lead mechanic who has proven credentials with carburetors (preferably SU carburetors); 4) Only if steps 1, 2 and 3 can't get the engine running properly should you consider removing the cylinder head.