Not getting full timing advance on 230TE. M102

[CEC]

The car is a 1985 230TE 123 chassis wagon. It uses the M102 engine. I decided today to check the timing as it probably hasn't been done in years. The car currently has 210,000 miles. I checked the base timing which was at about 10 degrees. My manual said it should be at 15 degrees base so I increased the timing to 15. It also instructed me to check the timing at 4500RPM. At that RPM with the vacuum attached I should be getting 40-45 degrees timing. Now as you can imagine an old M102 engine with a old exhaust humming at 4500RPM is quite loud. So I only checked it once. But I wasn't getting 40-45 degrees. I was getting in the 30's. Sorry don't have an exact since I didn't liquid paper 30-35. I did have 20 marked and 40 marked so I am guessing where it ended up. So it appears I am not getting my full timing advance. Any ideas or suggestions. Is it ok that I adjusted it at base timing and not at the 4500RPM level. According to 2 different manuals I should do my adjusting at 4500RPM but I am sure my neighbors wouldn't appreciate that at 9PM at night. Now I have checked timing for years on many cars but this is the first time I have ever had to check it at 4500RPM. Normally I just set the base. Can someone shed light on this for me? Any ideas why I am not getting full advance?

Chuck
1985 230TE 5 Speed