Converting from R12 to 134a was a mistake, 134a has only 75/80% the cooling capacity of a good R12 system, there should be a sticker under your hood that says what the R12 capacity of your air conditioning system is, when useing 134a you normally use 85/90% of whatever the R12 capacity is, the amount you stated in your post sounds like it could be over charged which will cause poor performance, you cannot use the site glass technique with a 134a conversion, you need to monitor the temp as it is being charged and stop at the lowest temp reading.