308GTSi QV stumbling up to 4000 RPM

Hey all, finally got my dream car I’ve wanted since I was 12 years old when the prominent art in my bedroom was the 308 and Farrah Fawcett. I have a tremendous history on service and the car was just coming out of 3 years of mechanical refresh by an excellent pro named Owen Tamburr with incredible documentation. The car sat for a long time - the PO bought it with 21,000 miles on it and put another 800 on it before it went down for mechanical service. I’ve put another 1000 on it in 2 months and It’s been great but suddenly started stumbling up to 3800 RPM and then, like a switch, it’s fine and zings from there. I checked as many connections as I could, and hoses I can see/reach are all tight. After a week of sitting, it’s worse today, never really getting happy. It acts like it’s “off the cam” on an older car. There’s no tach bounce, just not at full chat. I thought maybe a vacuum leak somewhere that’s progressing? I thought maybe a wiggling crank angle sensor? Basic ignition items were replaced a couple of years ago with only my use on them but they’re not new. I’m going to refresh them anyway. I have a lift coming in a week or so that will hopefully make things a bit easier. Any obvious things to check would be welcomed. Thanks -

 

Thanks! It’s a 1983. I did just get this from my friend the mechanic for the PO (he’s retired and 1300 miles away):

Ron, have you changed out the magnets for tdc and the front and rear banks? The spark plug extensions are notorious to burn through and intermittently short. Start the engine cold and listen…any snapping sound is an extension burnt though. The extensions can dance on the plug connections. A close visual inspection of a black mark on the extension will show the culprit. Check the condition of both dist. rotors and king leads. What fuel are you running… trash in the fuel or filter might be suspect. Check all connections at the ecu. and the vacuum lines at the throttle and CIS components.Ignition wires are always suspect as well especially if they are red sleeved. They can fall from their plastic holders on the valve covers. I will think more while watching Laguna Seca . O