In total Western part of India accounts for 101 seats from states of Maharashtra, Gujarat, Rajasthan and Goa.

In the 2014 elections, BJP swept all the seats in Gujarat, Rajasthan and Goa and its alliance with Shiva Sena swept the Maharashtra winning 42 of the 48 seats.  So BJP / NDA had won the 95 out of 101 seats in 2014, this one definitely can calls its peak performance.

In 2019, situation looks different, and do not expect to BJP/NDA repeat its 2014 performance and is one of the regions where it is expected to loose significant number of seats that will bring down its total tally in comparison to 2014.

Let us look at these states individually.

Gujarat
Total Parliamentary Seats - 26

In 2014, BJP had swept this state completely. In 2019, it is still expected that BJP will continue to do well in this home state of Narendra Modi and Amit Shah. But expected to loose few seats due to regional anti-incumbency. This is one of the state where it is a direct fight between BJP and Congress, hence probably easier to predict, and not much changes expected around election corner.

Indicative Seats tally
Total Seats - 26
BJP - 18 to 20
Congress - 6 to 8

Goa
Total Parliamentary Seats - 2

In 2014, BJP had won both the seats in this small Western State. But 2019 looks different, and there seems to be strong anti-incumbency. Add to this BJP Stalwart from the state Manohar Parrikar is not in good health and may not spend much time in the election campaign. Hence it is expected that BJP will not be retain both the seats

Indicative Seats tally
Total Seats - 2
BJP - 1
Congress - 1

Rajasthan
Total Parliamentary Seats - 25

In 2014, BJP had won all the seats in the state, back on the strong showing from 2013 Assembly elections. This time around there is strong anti-incumbency against BJP for the upcoming 2018 assembly elections which widely expected that Congress will wrest from BJP. However for the national election, there is still a strong sentiment in favor of Narendra Modi due to which BJP might still do well to maximum seats in this state

Indicative Seats tally
Total Seats - 25
BJP - 14 to 18
Congress - 6 to 10

Maharashtra
Total Parliamentary Seats - 48

Maharashtra is one of the biggest state in terms of number seats after the Uttar Pradesh (80 seats). As we can see the previous parliamentary election results, the party / Alliance that has done well in Maharashtra has gone on to rule in the Center. So it is critical for BJP / Congress to do well in this state. In 2014,  NDA had BJP, Shiva Sena and small regional parties and UPA had Congress and NCP.  Later in 2014 assembly elections all the major parties had contested separately and BJP had become the leading party and short of majority. It then had to get into alliance with Shiva Sena to form the government. From 2014 one thing is clear, BJP is grown significantly in this state and now can be classified as number 1 party which used to held by Congress earlier.  In 2019  - so far Congress and NCP have been telling the voters that are going to contest in alliance and some smaller regional parties from NDA will be shifting from NDA to UPA. In NDA BJP has still smaller regional parties, but bigger one Shiva Sena is acting tough and wants to content alone. Shiva Sena will not gain anything in number of seats by contesting alone, but it wants to bring down the BJP numbers significantly by doing this. It wants to be the big brother in the alliance, which is no longer the case since 2014.

So at this state predictions is based on the UPA (Congress + NCP), BJP and Shiva Sena contesting separately.

So indicative seat tally is,

Total Seats - 48
BJP - 15 to 20
UPA (Congress + NCP) - 25 to 30
Shiva Sena - 3 to 5

Summary

In summary, BJP/NDA cannot be expected to repeat their good show from the 2014 elections. They are expected to lose few seats in Gujarat, Rajasthan and majorly in Maharashtra due to alliance arithmetic. They can cut down their loss - if there is a alliance with Shiva Sena