diff --git a/pyren/mod_ecu.py b/pyren/mod_ecu.py
index 133625a..fdced12 100755
--- a/pyren/mod_ecu.py
+++ b/pyren/mod_ecu.py
@@ -152,8 +152,7 @@ class ECU:
     self.elm.start_session( self.ecudata['startDiagReq'] )
 
     if mod_globals.os == 'android' or mod_globals.opt_csv:
-      if self.ecudata['pin'].lower()=='can' and self.DataIds:
-        mod_globals.opt_perform = True
+      if self.ecudata['pin'].lower()=='can' and self.DataIds and mod_globals.opt_perform:
         self.elm.checkModulePerformaceLevel(self.DataIds)
 
     print "Done"  
diff --git a/pyren/mod_ecu_mnemonic.py b/pyren/mod_ecu_mnemonic.py
index 9e12803..7757644 100755
--- a/pyren/mod_ecu_mnemonic.py
+++ b/pyren/mod_ecu_mnemonic.py
@@ -64,7 +64,7 @@ def get_mnemonic( m, se, elm, raw = False ):
 
 def get_SnapShotMnemonic(m, se, elm, dataids):
   snapshotService = ""
-  byteLength = 3
+  byteLength = 3 #number of chars in one byte string (two chars with one whitespace)
   dataIdByteLength = 2
 
   for sid in se:
@@ -81,24 +81,35 @@ def get_SnapShotMnemonic(m, se, elm, dataids):
   numberOfIdentifiers = int("0x" + resp[7*byteLength:8*byteLength-1],16)
   resp = resp[8*byteLength:]
 
-  didDict = {}
+  didDict = {} #dataIds with their corresponding data
+  numberOfPossibleDataId = 0 #number of unknown dataIds
   posInResp = 0
-  dataIdLength = dataIdByteLength * byteLength
+  dataIdLength = dataIdByteLength * byteLength 
   
-  for x in range(numberOfIdentifiers):
+  for idNum in range(numberOfIdentifiers):
+    #break if unknown dataids number plus current number dataid number is larger than overall number of dataids in the response
+    if (idNum + numberOfPossibleDataId > numberOfIdentifiers):
+      break
+
     dataId = resp[posInResp:posInResp + dataIdLength].replace(" ", "")
     posInResp += dataIdLength
-    if dataId not in dataids.keys():
+    
+    if dataId not in dataids.keys(): #unknown dataId in the snapShot response
       bytePos = 1
       restOfResp = resp[posInResp:]
 
-      while True:
+      while True: #try to find a next dataId that is defined in the module file
         posInRestResp = bytePos*byteLength
+        
+        #using '2' as possible start of dataId is not the best approach, to fix in the future 
         if len(restOfResp) > posInRestResp + dataIdLength and restOfResp[posInRestResp] == '2':
+          numberOfPossibleDataId = numberOfPossibleDataId + 1
           possibleDataId = restOfResp[posInRestResp:posInRestResp + dataIdLength].replace(" ", "")
           if possibleDataId in dataids.keys():
             posInResp += posInRestResp
             break
+          else:
+            bytePos += 1  
         else:
           bytePos += 1
       continue
@@ -108,8 +119,8 @@ def get_SnapShotMnemonic(m, se, elm, dataids):
     posInResp += didDataLength*byteLength
     didDict[dataId] = didData
 
-  startByte = ""
-  startBit = ""
+  startByte = "1"
+  startBit = "0"
   dataId = ""
   for did in dataids.keys():
     for mn in dataids[did].mnemolocations.keys():
diff --git a/pyren/mod_ecu_parameter.py b/pyren/mod_ecu_parameter.py
index 1aadba8..618b717 100755
--- a/pyren/mod_ecu_parameter.py
+++ b/pyren/mod_ecu_parameter.py
@@ -15,7 +15,7 @@ def get_parameter( pr, mn, se, elm, calc, dataids = {} ):
 
   for m in sorted(pr.mnemolist, key=len, reverse=True):
     
-    if dataids:
+    if dataids and mn[m].request.startswith("22"):
       val = get_SnapShotMnemonic(mn[m], se, elm, dataids )
     else:
       val = get_mnemonic( mn[m], se, elm )
diff --git a/pyren/mod_ecu_state.py b/pyren/mod_ecu_state.py
index 53e1e0d..e86bd1f 100755
--- a/pyren/mod_ecu_state.py
+++ b/pyren/mod_ecu_state.py
@@ -11,7 +11,7 @@ def get_state( st, mn, se, elm, calc, dataids = {} ):
   comp = st.computation
   comp = comp.replace("&","&")
   for m in sorted(st.mnemolist, key=len, reverse=True):
-    if dataids:
+    if dataids and mn[m].request.startswith("22"):
       hex_val = get_SnapShotMnemonic(mn[m], se, elm, dataids )
     else:
       hex_val = get_mnemonic( mn[m], se, elm )
diff --git a/pyren/pyren.py b/pyren/pyren.py
index 6bb7b5c..63592a2 100755
--- a/pyren/pyren.py
+++ b/pyren/pyren.py
@@ -196,6 +196,12 @@ def optParser():
       default=False,
       action="store_true")
 
+  parser.add_argument("--perform",
+      help="use UDS performance mode, not fully developed yet",
+      dest="perform",
+      default=False,
+      action="store_true")
+
   options = parser.parse_args()
   
   if not options.port and mod_globals.os != 'android':
@@ -231,6 +237,7 @@ def optParser():
     mod_globals.opt_exp       = options.exp
     mod_globals.opt_dump      = options.dump
     mod_globals.opt_can2      = options.can2
+    mod_globals.opt_perform   = options.perform
     mod_globals.opt_sd        = options.sd
     if options.dev=='' or len(options.dev)!=4 or options.dev[0:2]!='10':
       mod_globals.opt_dev       = False