I just use my body weight and a bit of maths to do the sum to know where to stand on my breaker bar plus extension. It seems to work. But obvs far better to have the proper kit!

Have you checked the connectors for bent pins ?

count the threads left out from the locknut on the wastegate rod, if there are less than 12 adjust it to 12 and see then with F2 removed but if it's a noticeabe difference with fuse removed than with it in place replace the wastegate modulator...

Modified seat rail details:

What did the 4 wheel alignment show ? Things like castor, camber etc. Never accept "it was OK" - as each side can be in tolerance, but different

Have you got the correct length adjustable length panhard rod ? If not, the axle will be pulled to one side. There are 2 production rods with quite a significant difference in length between them. When the rod length was changed the axle mounting...