My 3gs is going through oil faster than it should at 134,000 miles. I do have a slight oil leak but i dont think it would justify the amount of oil im losing. I'm planning on changing the pcv valve but I'm also looking into a fuel injection service. Does anyone even reccomend a fuel injection service or is it a waste of time? Any input would be appreciated.

Your oil burning has nothing to do with dirty injectors. If you have oil leaks, I would fix them. How often are you changing your oil? Usually oil issues happen when oil isnt changed as often, results in a dirtier engine internals. When dirt, grime, block the piston oil rings control rings then that engine oil passes into the combustion chamber.

What I would do, fix that external oil leak. Change your oil at every 3,000 miles and use oem filter. Any good decent oil is fine, theres not need to spend big money on expensive synthetic oils. I use castrol gtx its synthetic blend, and my 08 GS350 has over 210k miles and I burn 1/2 quart every 3,000 miles.

Is there a specific service that would reduce/prevent burning oil?

The issue is a design flaw with lexus and toyota pistons when they started to introduce 5,000 mile oil changes. The longer you allow used oil in an engine the more deposits that engine collects. The issue is with the pistons, oil control rings the poor design allows the grime to gum up those rings, and once the oil rings are gummed up then that grime goes to the combustion rings locking those rings into the piston.

The solution is easy, replace your oil at 3,000 miles. Use oem oil filter! Any good known brand oil is fine, just change it early. You can use a product called BG moa and epr. This helps clean the inside oil galleries. The service lexus recommends is to do a full engine rebuild.