Why does my 2018 mustang GT run like a dog lately...it ha...

Why does my 2018 mustang GT run like a dog lately...it has a Roush tune with the CAI and axle back [exhaust](/topics-exhaust-ford/)..all Roush products ..it used to run awesome until about a month ago and now feels very sluggish ...

Why does my 2018 mustang GT run like a dog lately...it has a Roush tune with the CAI and axle back [exhaust](/topics-exhaust-ford/)..all Roush products ..it used to run awesome until about a month ago and now feels very sluggish Mechanic's Assistant: How many miles are on the Shelby? How has your [mileage](/topics-mileage-ford/) been lately? It’s not a Shelby it’s a Mustang HT with the 10 r80 [transmission](/topics-transmission-ford/) with 12,500 miles I bought it new in 2018 Mechanic's Assistant: Are you fixing your Mustang GT yourself? What have you tried so far? Yes ... just cleaned the CAI and it’s air filter is all I’ve done and octane boost just in case it was a bad tank of gas Mechanic's Assistant: Anything else you want the Mechanic to know before I connect you? That’s about it for now

Automotive Expert
Hello and thank you for using JustAnswer. My name is \*\*\*\*\* \*\*\*\*\* I will do my best to assist you. During this conversation you will be given an automated offer for a phone call. You may accept or decline that offer.I don’t personally offer this service so if you take this another tech may call I’m sorry that you’re having trouble with your vehicle. I will do my best to help you resolve them. Please understand that I do not know your knowledge or capabilities so I may need to ask questions to find out basic information to help solve your specific problem. My aim is to give you the best service possible and to help you. If you have any questions or concerns, please don’t hesitate to let me know. Sometimes it may take a moment for me to respond because I may have to look up information about your concern. I appreciate your patience and will provide responses as soon as possible. I can tell you the factory air intake is extremely good in the 18-up GT so you may be experiencing hot intake temps because of the roush cold air is taking in more hot air if you live in a hotter climate. Other than that it could be so many things but I would look for a vacuum leak or maybe a loose hose coupler on the intake. Did this start after the cold air intake?

I've had the cold air intake for over a year and for the most part it's been running really strong especially since I added the Roush axle back exhaust wich I was very surprised over cause I didn't think that addition would help performance wise but it seemed to compliment well ..Cold air temps have been low I live in New Jersey ..I added the axle back in June
Automotive Expert
Well then I would be looking for a loose coupler or vacuum leak. And if this is a custom tune I would contact the tuner. They will likely have you do a datalog with the handheld tuner so they can look at fuel trims, timing, ect.... If you dont have a custom tune I highly recommend one on the 18-up cars. It really wakes them up and will likely fix your issue.

I have a Roush tune that was done by the dealer ... I know I could take it back to them ..just trying to avoid that cause I won't have an appointment for at least a couple of weeks .. but do you think a custom tune would be better than a Roush ? .. I got the Roush trying to be smart to hold the warranty but at this point I don't care anymore..it's my first toy in 20 years so I'm just having fun with it .. before this I always mustangs 5.0's from the 80's and 90 fox body's a 70 Mach 1 even a viper so I get the gist but just playing catch-up on the tech so to speak
Automotive Expert
Yes a custom tune is way better. The roush factory style tune is a very safe tune an there is power left on the table. I suggest Lund Racing or Palm Beach Dyno. Those are your 2 top coyote tuners. I have a 16 Gt myself and use Lund.

I'll search for a vacuum leak sounds like the most probable cause being that I feel like I lost so much bottom end torque..
Automotive Expert
Very well could be. Check the mass air flow sensor also. Make sure it is plugged in and the screws are tight.

Ok ���� will do ... if I have any questions while I'm work on this can I text you back at this number ? I'm Tim by the way
Automotive Expert
Hey Tim yes you can just message me back here. I will leave the question open.

Thanks ����

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