Squeezing some extra speed out of my line?

[#1]

Hi Guys,
Was just wondering if anyone could offer some hints, Im not very versed in 'good' snr and attenuation ratios so if someone could look at my stats it would be much appreciated
Had fibre installed about 2 weeks ago, new faceplate and a data extension installed by openreach, The data extension is only about 4 metres long to be fair
On installation day I was syncing at around 25mbps. Now i seem to have dropped to around 21.8mbps, having tried in the master test socket its around 21.9mbps so fairly sure the data extension is having no major effects.
Sometimes I do hear a slight crackle on the line during calls and wondered if this is something that can be fixed at all? To be fair we had a few issues with our line over the years and the bt test always used to say 'High Loop Resistance' whatever that may mean! Even on ADSL when my line was supposed to be 7mbps we struggled to 5mbps.
Here are my Hub One stats if anyone can tell me what part of it may be causing the issue:
6. Data rate: 2000 / 22398
7. Maximum data rate: 3362 / 26504
8. Noise margin: 7.3 / 6.4
9. Line attenuation: 31.0 / 28.7
10. Signal attenuation: 30.9 / 25.4
11. Data sent/received: 204.9 MB / 2.3 GB
12. Broadband username: ***********@plusdsl.net
13. 2.4 GHz Wireless network/SSID: ISS-2.4GHZ
14. 2.4 GHz Wireless connections: Enabled (802.11 b/g/n (up to 300 Mb/s))
15. 2.4 GHz Wireless security: WPA2
16. 2.4 GHz Wireless channel: Automatic (Smart Wireless)
17. 5 GHz Wireless network/SSID: ISS-5GHZ
18. 5 GHz Wireless connections: Enabled (802.11 a/n/ac (up to 1300 Mb/s))
19. 5 GHz Wireless security: WPA2
20. 5 GHz Wireless channel: Automatic (Smart Wireless)
21. Firewall: Default
22. MAC Address: **:**:**:**:**
23. Modulation: G.993.2 Annex B
Many thanks to all and wishing you all a Merry Christmas
Lee

[#2]

I've mentioned it in previous posts, but what is your BT Master socket like? Mine until recently, was 15 years old. I essentially replaced the entire socket box myself (except the back plate) with a brand new MK3 Openreach VDSL plate with built in filter and also, the lower part of the NTE5 box with a brand new part with the bell line filter, something the old box didn't have. Combined with a short 1 metre fully shielded professional grade dsl cable from Tandy, I'm very pleased with my speed and connection through my Home hub 5. No drop outs. Yes, it cost me the best part of £20 to 'self help', but in my view, it was worth it as unlike my previous BT fibre connection, my Plusnet connection is now rock solid.