Subject Awaiting Garbage Collector

I'll try explain the situation in which we are in the shortest way possible...

We're using a software in our company made by some people in Spain, the software supports 70 simultaneous users and we are experiencing slowness using the software so I started the investigation, and not later found that our database was increasing awaiting garbage transactions every second, as after 4 or 5 hours the number of awaiting transactions are up to 90.000. I've been reading about Firebird and its retaining legacy commit and performance degradation, but no one tells if 10.000 or 20.000 or even 100.000 awaiting gc transactions could be the reason of the poor software performance. I have confirmation from the programmer that the component used to connect to firebird is DEVART IBDAC, with the AutoCommit flag set to TRUE
. We have a Firebird 2.5 Classic Server,and also tried with Super Classic server architecture, but no difference, on a linux box, plenty of RAM and CPU and disk speed. 

I'm using Sintatica to monitor the database. Sinatica only tells the amount of transactions that are awaiting GC. I would like to know the amount of transactions awaiting gc per user or per connection, so I can know which client is piling up the most of transactions. Is there a system table or another software monitor that could tell me that information?

Thank you!!