I checker the RPM of the Sonic . It is in the 700's .

Looked at some other data , but will have to study it to try to make some sense of it .

Do you have a set of gauges to check the A/C ? The A/C could account for some load . Did you say it was a manual or automatic tranny ?

Does the A/C perform well ? At the age of the car , it could need some refrigerant , but best to put gauges on it .

Here is a report Torque Generated , do not know what it will help or not ?

Mode $06 report generated by Torque for Android
================================================

Vehicle VIN: Not present
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: Not present

Test report:
------------------
MID:$01 TID:$01
Rich to Lean sensor threshold voltage(constant) - O2 Bank 1 Sensor 1
Max: 0.45018V Min: 0.45018V
Test result value: 0.45018V
PASS
----
MID:$01 TID:$02
Lean to Rich sensor threshold voltage(constant) - O2 Bank 1 Sensor 1
Max: 0.45018V Min: 0.45018V
Test result value: 0.45018V
PASS
----
MID:$01 TID:$03
Low sensor Voltage for switch time calculation - O2 Bank 1 Sensor 1
Max: 0.40016V Min: 0.40016V
Test result value: 0.40016V
PASS
----
MID:$01 TID:$04
High sensor Voltage for switch time calculation - O2 Bank 1 Sensor 1
Max: 0.60036V Min: 0.60036V
Test result value: 0.60036V
PASS
----
MID:$01 TID:$05
Rich to Lean sensor switch time(calculated) - O2 Bank 1 Sensor 1
Max: 108ms Min: 0ms
Test result value: 38ms
PASS
----
MID:$01 TID:$06
Lean to Rich sensor switch time(calculated) - O2 Bank 1 Sensor 1
Max: 156ms Min: 0ms
Test result value: 12ms
PASS
----
MID:$02 TID:$8b
- O2 Bank 1 Sensor 2
Max: 7.99527V Min: 0.77531V
Test result value: 0.77568V
PASS
----
MID:$02 TID:$8c
- O2 Bank 1 Sensor 2
Max: 0.10004V Min: 0V
Test result value: 0.05112V
PASS
----
MID:$02 TID:$91
- O2 Bank 1 Sensor 2
Max: 0.45018V Min: 0V
Test result value: 0.42541V
PASS
----
MID:$02 TID:$92
- O2 Bank 1 Sensor 2
Max: 7.99527V Min: 0.35014V
Test result value: 0.38723V
PASS
----
MID:$02 TID:$93
- O2 Bank 1 Sensor 2
Max: 8 Min: 0
Test result value: 1.01
PASS
----
MID:$02 TID:$94
- O2 Bank 1 Sensor 2
Max: 8 Min: 0
Test result value: 0.35
PASS
----
MID:$21 TID:$a0
- Catalyst Monitor Bank 1
Max: 3.99977 Min: 0.34983
Test result value: 0.95252
PASS
----
MID:$35 TID:$b0
-
Max: 100Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$35 TID:$b1
-
Max: 100Count Min: 0Count
Test result value: 0Count
PASS
----


God bless
Wyr