2011 Vauxhall Insignia 2011 2.8 power steering not working below 3000 rpm

Incredibly heavy until 3000 rpm, had 2 x recon pumps replaced - reluctant to replace rack (£800 inc labour - 2 weeks wait) without a clear diagnosis of the problem. Thanks in advance. No leaks, oil good happened after full lock on RH side! Worked initially after 1st pump replaced then back to not working until 3000rpm. 2nd (original) pump didnt work til after 3000rpm from replacement