Resolved Memory problems after migration

Hello,

I'm currently migrating a customers site from J3/VM3 to J4/VM4. One of the last things remaining is to get CSVI working and I really got stuck here....
On the current site CSVI has been running for ages without any problems. It is used to export product data as XML file for Google. The produced output file
contains around 6000 records. The current versions are J3,VM3 CSVI 7.20.0.
I've now migrated the site (on a local server) to J4/VM4.2.4. I then updated CSVI to the current version 8.9.2. Although I'm on a local server with 512M memory,
I seem to run into memory limit problems. On the LIVE site the memory limit is 256M (and can't be increased any further) and was always sufficiant. On a preview server where I also tested, the process sometimes comes up with status 200 OK, but then throws warnings about Virtuemart varaibles.
Can it really be the case that 512M are not enough memory for the current version of CSVI? Or might there be a different problem involved?
I'm really stuck now (can't put the site online) and would appreciate any help/hints.

Kind regards,

Petra