I let the fuel get lower than I ever have in my '86 951(into the red), and after filling up it started to have hard start issues. When cold it would take 3 or 4 tries with sputtering and stalling until it would finally sputter and then run well. Hot it would just take a few more revolutions than normal. After a couple days the hard start issues have gone away but today it started to sputter/pop through the exhaust under hard throttle, but run perfectly otherwise. I'm thinking it picked up a lot of trash when the tank was so low and I plan to replace the fuel filter tomorrow, but if you guys have any other input/advice I'm all ears. Thanks!

 

I think you and I are having the same issue. What may be happening is debris from the tank may be restricting the strainer in the tank and causing a lean fuel condition at the engine. You'll need to pull the fuel pump, filter and strainer to do it right. That means draining most all of the fuel out of the tank so you won't flood the garage. Pull the strainer (it is threaded and twists out) and then using the access for the fuel sender in the cargo area, flush the tank out. A garden hand sprayer works great. I'd use kerosene because it has a higher flash point and is compatible with gasoline when you refill the tank. Water is, well....NOT. Replace the strainer gasket, Fuel filter and in my case, just to be sure, the fuel pump (if it's an old one) as well.

 

The gunk could have made it into the injectors - you can clean them on the bench or send them off. A lot of people have good experiences with Witch Hunter, I think it's less than $100 all in. There are some good DIY injector cleaning videos on youtube if you want to take that route.