Airspeed troubles
I went thru similar travails with my 6A a/s .
Getting the A&P to do a pitot static check on my system gave absolute direction to solving my issues.The equipment used is more useful than I thought at solving pitot-static issues. For $100 I solved many hours of small issues. I strongly recommend it.
1>A small leak at the pitot wing-to-fuselage junction.
2>New behind the panel push-on tubing onto barbed fittings as opposed to original leaky Nylok style fittings/tubes eliminated a few suspect areas
3>The A/S indicator was replaced because the original one leaked excessively. It was an imported mph TAS style where you can set temp on a scale to get TAS. It seemed to indicate low as if it were a knots mechanism with a mph face. Anyway, I tossed it and the new one works great.