Apologies for the long post but I am hoping the TVWBB restoration experts can help me. I'm having insufficient heat issues with my 1980s Genesis 3 that I restored several years ago. I can only get the grill up to 375F or so, but I used to get it to just over 500F. I'm aware of bypass mode and make sure I don't open manifold valves and ignite until a minute or so after opening propane tank. I've cleaned out burner tubes, spider guards and venturis. I just replaced the regulator with a heavier duty Precimex (did the hose too). I used yellow sealing tape and cannot find any leaks.
At this point I'm thinking the manifold may be an issue. I'm not 100% sure as I got the grill about 23 years ago but I believe the manifold is original. It is the round type with two flat brackets that bolt to the fire box; the tubular part of the manifold hangs from the frame with a single stamped steel bracket. The valves are a bit sticky but it was working well earlier this year. I've also added brass fittings so I can use this old manifold with modern QCC1 regulator hoses such as the new one I just put on.
I've been unable to find a parts diagram for model 430000 but Weber tells me that I can rely on the schematic for model 471001 - a newer grill that I don't fully trust is the same. This parts diagram tells me that the manifold is Weber part # 56038 which I don't think is right as it has a square (not round) manifold tube and two wire hangers (and not the single steel bracket).
My question for the group is what Weber manifolds will I be able to fit to this grill and firebox? The square shape of Weber # 56038 may be a problem but has anyone fitted one of these to an old Genesis 3? I also see that Weber # 90383 (from a genesis gold/silver C) might work as it looks similar (and I really need the side burner connection). Any help in identifying a manifold that I can use would be very much appreciated!
Pics of my favorite Weber below:


At this point I'm thinking the manifold may be an issue. I'm not 100% sure as I got the grill about 23 years ago but I believe the manifold is original. It is the round type with two flat brackets that bolt to the fire box; the tubular part of the manifold hangs from the frame with a single stamped steel bracket. The valves are a bit sticky but it was working well earlier this year. I've also added brass fittings so I can use this old manifold with modern QCC1 regulator hoses such as the new one I just put on.
I've been unable to find a parts diagram for model 430000 but Weber tells me that I can rely on the schematic for model 471001 - a newer grill that I don't fully trust is the same. This parts diagram tells me that the manifold is Weber part # 56038 which I don't think is right as it has a square (not round) manifold tube and two wire hangers (and not the single steel bracket).
My question for the group is what Weber manifolds will I be able to fit to this grill and firebox? The square shape of Weber # 56038 may be a problem but has anyone fitted one of these to an old Genesis 3? I also see that Weber # 90383 (from a genesis gold/silver C) might work as it looks similar (and I really need the side burner connection). Any help in identifying a manifold that I can use would be very much appreciated!
Pics of my favorite Weber below:

