I know it's dam hard to diagnose without seeing it, I'm basically hoping for suggestions on what to check, sometimes someone will make a suggestion of something I've not thought of.It's very difficult to diagnose a vehicle without seeing it.
My brother had an issue with his girlfriend's car, He jumped to the conclusion it was a gearbox/clutch issue. Had a look at the car myself, Shaked the engine & said 'Is that the noise?'. Yes he replied, Got the car on some stands & the exhaust heat shield had broken off. So was knocking on the exhaust, So just goes to show it can be the most simple of things sometimes!