Pelican Parts Forums - intermittent problem with my 944S

I've got an '87 944S with an intermittent problem. Sometimess it will run very smooth just like it should. Other times it will run rough at all engine speeds. Other times it will run rough only from idle to 3000 rpm. When it runs rough it hesitates on acceleration and sputters when it idles. If it starts off smooth about 20 minutes later it will run rough, then a while later it will run smooth. If it starts off rough it will smooth out a while later. If it has been sitting outside in the warm sun for a couple hours it will not start right away. It will start and immediately stop. It will start and stop about three times and then it will start right up and stay running. If it is sitting inside or in shade it will not have a problem starting. Other than the starting problem it has never quit running on me. It has all new belts- timing and balance too, as well as chain tensioner. Spark plugs are not old at all, nor is the air filter, new dme relay. I tossed some Techron in the tank and I use Chevron gas- alway 91 octane. When it hesitates on acceleration it feels like the engine isn't getting the gas it wants- like a clogged fuel filter. Could a bad fuel filter cause all this?? I don't know when the fuel filter was replaced last. I was wondering if the starting in the sun thing could be caused by a faulty coolant temp sensor??? Any help is greatly appreciated.