I have two problems that I don't think are related, but might be...you decide. The most pressing issue is that if I try to accelerate with the RPMs (I have a manual trans) below 2250, the engine stutters kind of like it's missing or the mixture is too rich (or when you try to shift too early). It wasn't doing this before and started happening soon after I took it to the dealership for a service (big, big, big, mistake that I will never make again!!!). The second issue is that, unless I have the highest octane fuel going through the engine, I get what sounds like valves rattling when the engine is under load at higher speeds. I'm thinking I could do a few things to try and fix this: clean the MAF sensor, change plugs and wires, put in a new oxygen sensor. Thoughts? Thanks in advance for your advice.